21365690 has 32 divisors (see below), whose sum is σ = 40824000. Its totient is φ = 8028288.

The previous prime is 21365657. The next prime is 21365699. The reversal of 21365690 is 9656312.

21365690 = 321² + 322² + ... + 459².

It is a happy number.

It is a super-2 number, since 2×21365690² = 912985418352200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21365699) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26006 + ... + 26814.

It is an arithmetic number, because the mean of its divisors is an integer number (1275750).

Almost surely, 2^21365690 is an apocalyptic number.

21365690 is a deficient number, since it is larger than the sum of its proper divisors (19458310).

21365690 is a wasteful number, since it uses less digits than its factorization.

21365690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 974.

The product of its (nonzero) digits is 9720, while the sum is 32.

The square root of 21365690 is about 4622.3035382805. The cubic root of 21365690 is about 277.4846567823.

The spelling of 21365690 in words is "twenty-one million, three hundred sixty-five thousand, six hundred ninety".