21992639 has 2 divisors, whose sum is σ = 21992640. Its totient is φ = 21992638.

The previous prime is 21992629. The next prime is 21992653. The reversal of 21992639 is 93629912.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21992639 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21992596 and 21992605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21992629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10996319 + 10996320.

It is an arithmetic number, because the mean of its divisors is an integer number (10996320).

Almost surely, 2^21992639 is an apocalyptic number.

21992639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21992639 is an equidigital number, since it uses as much as digits as its factorization.

21992639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 52488, while the sum is 41.

The square root of 21992639 is about 4689.6310089388. The cubic root of 21992639 is about 280.1726783499.

The spelling of 21992639 in words is "twenty-one million, nine hundred ninety-two thousand, six hundred thirty-nine".