21610521 has 6 divisors (see below), whose sum is σ = 31215210. Its totient is φ = 14407008.

The previous prime is 21610507. The next prime is 21610541. The reversal of 21610521 is 12501612.

21610521 is a `hidden beast` number, since 2 + 1 + 610 + 52 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 21206025 + 404496 = 4605^2 + 636^2 .

It is not a de Polignac number, because 21610521 - 2⁵ = 21610489 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21610494 and 21610503.

It is not an unprimeable number, because it can be changed into a prime (21610541) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1200576 + ... + 1200593.

It is an arithmetic number, because the mean of its divisors is an integer number (5202535).

Almost surely, 2^21610521 is an apocalyptic number.

It is an amenable number.

21610521 is a deficient number, since it is larger than the sum of its proper divisors (9604689).

21610521 is a wasteful number, since it uses less digits than its factorization.

21610521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2401175 (or 2401172 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21610521 is about 4648.7117570355. The cubic root of 21610521 is about 278.5405394885.

The spelling of 21610521 in words is "twenty-one million, six hundred ten thousand, five hundred twenty-one".