621540 has 48 divisors (see below), whose sum is σ = 1935360. Its totient is φ = 165600.

The previous prime is 621527. The next prime is 621541. The reversal of 621540 is 45126.

It is a happy number.

621540 is a `hidden beast` number, since 621 + 5 + 40 = 666.

It is a hoax number, since the sum of its digits (18) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an Ulam number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 621540.

It is not an unprimeable number, because it can be changed into a prime (621541) by changing a digit.

621540 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36 + ... + 1115.

It is an arithmetic number, because the mean of its divisors is an integer number (40320).

2⁶²¹⁵⁴⁰ is an apocalyptic number.

621540 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 621540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (967680).

621540 is an abundant number, since it is smaller than the sum of its proper divisors (1313820).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

621540 is a wasteful number, since it uses less digits than its factorization.

621540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1169 (or 1161 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 621540 is about 788.3780818871. The cubic root of 621540 is about 85.3407315092.

Adding to 621540 its reverse (45126), we get a palindrome (666666).

The spelling of 621540 in words is "six hundred twenty-one thousand, five hundred forty".