21402690 has 32 divisors (see below), whose sum is σ = 51506496. Its totient is φ = 5691840.

The previous prime is 21402653. The next prime is 21402713. The reversal of 21402690 is 9620412.

It is a super-2 number, since 2×21402690² = 916150278472200, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21402690.

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, 14004 + ... + 15456.

It is an arithmetic number, because the mean of its divisors is an integer number (1609578).

Almost surely, 2^21402690 is an apocalyptic number.

21402690 is an abundant number, since it is smaller than the sum of its proper divisors (30103806).

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

21402690 is a wasteful number, since it uses less digits than its factorization.

21402690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1954.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21402690 is about 4626.3041404560. The cubic root of 21402690 is about 277.6447422810.

The spelling of 21402690 in words is "twenty-one million, four hundred two thousand, six hundred ninety".