21001960 has 64 divisors (see below), whose sum is σ = 54587520. Its totient is φ = 7123200.

The previous prime is 21001943. The next prime is 21001961. The reversal of 21001960 is 6910012.

It is not an unprimeable number, because it can be changed into a prime (21001961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29610 + ... + 30310.

It is an arithmetic number, because the mean of its divisors is an integer number (852930).

Almost surely, 2^21001960 is an apocalyptic number.

21001960 is a gapful number since it is divisible by the number (20) 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 21001960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27293760).

21001960 is an abundant number, since it is smaller than the sum of its proper divisors (33585560).

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

21001960 is a wasteful number, since it uses less digits than its factorization.

21001960 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 826 (or 822 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21001960 is about 4582.7895434986. The cubic root of 21001960 is about 275.9010006907.

Adding to 21001960 its reverse (6910012), we get a palindrome (27911972).

The spelling of 21001960 in words is "twenty-one million, one thousand, nine hundred sixty".