21705264 has 120 divisors (see below), whose sum is σ = 70760352. Its totient is φ = 6082560.

The previous prime is 21705241. The next prime is 21705269. The reversal of 21705264 is 46250712.

It is a super-2 number, since 2×21705264² = 942236970619392, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21705269) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 61312 + ... + 61664.

Almost surely, 2^21705264 is an apocalyptic number.

21705264 is a gapful number since it is divisible by the number (24) 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 21705264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35380176).

21705264 is an abundant number, since it is smaller than the sum of its proper divisors (49055088).

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

21705264 is a wasteful number, since it uses less digits than its factorization.

21705264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 435 (or 426 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21705264 is about 4658.8908551285. The cubic root of 21705264 is about 278.9469972927.

Adding to 21705264 its reverse (46250712), we get a palindrome (67955976).

The spelling of 21705264 in words is "twenty-one million, seven hundred five thousand, two hundred sixty-four".