21237639 has 8 divisors (see below), whose sum is σ = 28368240. Its totient is φ = 14132736.

The previous prime is 21237637. The next prime is 21237661. The reversal of 21237639 is 93673212.

It is a happy number.

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

It is not a de Polignac number, because 21237639 - 2¹ = 21237637 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21237637) 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 7 ways as a sum of consecutive naturals, for example, 4404 + ... + 7865.

It is an arithmetic number, because the mean of its divisors is an integer number (3546030).

Almost surely, 2^21237639 is an apocalyptic number.

21237639 is a deficient number, since it is larger than the sum of its proper divisors (7130601).

21237639 is a wasteful number, since it uses less digits than its factorization.

21237639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12849.

The product of its digits is 13608, while the sum is 33.

The square root of 21237639 is about 4608.4312949202. The cubic root of 21237639 is about 276.9291959771.

The spelling of 21237639 in words is "twenty-one million, two hundred thirty-seven thousand, six hundred thirty-nine".