21525690 has 32 divisors (see below), whose sum is σ = 51788160. Its totient is φ = 5726144.

The previous prime is 21525667. The next prime is 21525703. The reversal of 21525690 is 9652512.

It is a happy number.

It is a super-2 number, since 2×21525690² = 926710659952200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18856 + ... + 19964.

It is an arithmetic number, because the mean of its divisors is an integer number (1618380).

Almost surely, 2^21525690 is an apocalyptic number.

21525690 is an abundant number, since it is smaller than the sum of its proper divisors (30262470).

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

21525690 is a wasteful number, since it uses less digits than its factorization.

21525690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1766.

The product of its (nonzero) digits is 5400, while the sum is 30.

The square root of 21525690 is about 4639.5786446616. The cubic root of 21525690 is about 278.1755959796.

The spelling of 21525690 in words is "twenty-one million, five hundred twenty-five thousand, six hundred ninety".