21437690 has 16 divisors (see below), whose sum is σ = 38703528. Its totient is φ = 8549376.

The previous prime is 21437639. The next prime is 21437701. The reversal of 21437690 is 9673412.

It can be written as a sum of positive squares in 4 ways, for example, as 19882681 + 1555009 = 4459^2 + 1247^2 .

It is a super-2 number, since 2×21437690² = 919149105072200, which contains 22 as substring.

It is a plaindrome in base 11.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 494 + ... + 6566.

Almost surely, 2^21437690 is an apocalyptic number.

21437690 is a deficient number, since it is larger than the sum of its proper divisors (17265838).

21437690 is a wasteful number, since it uses less digits than its factorization.

21437690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6433.

The product of its (nonzero) digits is 9072, while the sum is 32.

The square root of 21437690 is about 4630.0853123890. The cubic root of 21437690 is about 277.7960047892.

The spelling of 21437690 in words is "twenty-one million, four hundred thirty-seven thousand, six hundred ninety".