21034240 has 36 divisors (see below), whose sum is σ = 50386644. Its totient is φ = 8413184.

The previous prime is 21034231. The next prime is 21034249. The reversal of 21034240 is 4243012.

It is an interprime number because it is at equal distance from previous prime (21034231) and next prime (21034249).

It can be written as a sum of positive squares in 2 ways, for example, as 15872256 + 5161984 = 3984^2 + 2272^2 .

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21034249) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6937 + ... + 9496.

It is an arithmetic number, because the mean of its divisors is an integer number (1399629).

Almost surely, 2^21034240 is an apocalyptic number.

21034240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21034240 is an abundant number, since it is smaller than the sum of its proper divisors (29352404).

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

21034240 is an equidigital number, since it uses as much as digits as its factorization.

21034240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16454 (or 16440 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21034240 is about 4586.3100636568. The cubic root of 21034240 is about 276.0422815571.

Adding to 21034240 its reverse (4243012), we get a palindrome (25277252).

The spelling of 21034240 in words is "twenty-one million, thirty-four thousand, two hundred forty".