21690690 has 32 divisors (see below), whose sum is σ = 59495040. Its totient is φ = 4957824.

The previous prime is 21690653. The next prime is 21690703. The reversal of 21690690 is 9609612.

It is a happy number.

It is a super-2 number, since 2×21690690² = 940972065352200, which contains 22 as substring.

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, 51435 + ... + 51854.

It is an arithmetic number, because the mean of its divisors is an integer number (1859220).

Almost surely, 2^21690690 is an apocalyptic number.

21690690 is an abundant number, since it is smaller than the sum of its proper divisors (37804350).

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

21690690 is a wasteful number, since it uses less digits than its factorization.

21690690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103306.

The product of its (nonzero) digits is 5832, while the sum is 33.

The square root of 21690690 is about 4657.3264863009. The cubic root of 21690690 is about 278.8845503247.

The spelling of 21690690 in words is "twenty-one million, six hundred ninety thousand, six hundred ninety".