21385690 has 8 divisors (see below), whose sum is σ = 38494260. Its totient is φ = 8554272.

The previous prime is 21385681. The next prime is 21385703. The reversal of 21385690 is 9658312.

It can be written as a sum of positive squares in 2 ways, for example, as 20169081 + 1216609 = 4491^2 + 1103^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21385690² = 914695473552200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1069275 + ... + 1069294.

Almost surely, 2^21385690 is an apocalyptic number.

21385690 is a deficient number, since it is larger than the sum of its proper divisors (17108570).

21385690 is a wasteful number, since it uses less digits than its factorization.

21385690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2138576.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 21385690 is about 4624.4664557114. The cubic root of 21385690 is about 277.5712124140.

The spelling of 21385690 in words is "twenty-one million, three hundred eighty-five thousand, six hundred ninety".