21705516 has 48 divisors (see below), whose sum is σ = 64314880. Its totient is φ = 6201360.

The previous prime is 21705503. The next prime is 21705517. The reversal of 21705516 is 61550712.

It is a super-2 number, since 2×21705516² = 942258849652512, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21705516.

It is not an unprimeable number, because it can be changed into a prime (21705517) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13600 + ... + 15111.

Almost surely, 2^21705516 is an apocalyptic number.

It is an amenable number.

21705516 is an abundant number, since it is smaller than the sum of its proper divisors (42609364).

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

21705516 is a wasteful number, since it uses less digits than its factorization.

21705516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28731 (or 28723 counting only the distinct ones).

The product of its (nonzero) digits is 2100, while the sum is 27.

The square root of 21705516 is about 4658.9179001137. The cubic root of 21705516 is about 278.9480768214.

The spelling of 21705516 in words is "twenty-one million, seven hundred five thousand, five hundred sixteen".