21525813 has 12 divisors (see below), whose sum is σ = 31168800. Its totient is φ = 14315496.

The previous prime is 21525793. The next prime is 21525853. The reversal of 21525813 is 31852512.

It is a happy number.

It is not a de Polignac number, because 21525813 - 2¹³ = 21517621 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21525853) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1288 + ... + 6686.

It is an arithmetic number, because the mean of its divisors is an integer number (2597400).

Almost surely, 2^21525813 is an apocalyptic number.

It is an amenable number.

21525813 is a deficient number, since it is larger than the sum of its proper divisors (9642987).

21525813 is a wasteful number, since it uses less digits than its factorization.

21525813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5848 (or 5845 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 21525813 is about 4639.5919001567. The cubic root of 21525813 is about 278.1761258199.

The spelling of 21525813 in words is "twenty-one million, five hundred twenty-five thousand, eight hundred thirteen".