21537690 has 16 divisors (see below), whose sum is σ = 51690528. Its totient is φ = 5743376.

The previous prime is 21537689. The next prime is 21537743. The reversal of 21537690 is 9673512.

It is a super-2 number, since 2×21537690² = 927744181072200, which contains 22 as substring.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 358932 + ... + 358991.

It is an arithmetic number, because the mean of its divisors is an integer number (3230658).

Almost surely, 2^21537690 is an apocalyptic number.

21537690 is an abundant number, since it is smaller than the sum of its proper divisors (30152838).

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

21537690 is a wasteful number, since it uses less digits than its factorization.

21537690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 717933.

The product of its (nonzero) digits is 11340, while the sum is 33.

The square root of 21537690 is about 4640.8716853626. The cubic root of 21537690 is about 278.2272782105.

The spelling of 21537690 in words is "twenty-one million, five hundred thirty-seven thousand, six hundred ninety".