20812639 has 2 divisors, whose sum is σ = 20812640. Its totient is φ = 20812638.

The previous prime is 20812621. The next prime is 20812699. The reversal of 20812639 is 93621802.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20812639 - 2⁷ = 20812511 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20812639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20812699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10406319 + 10406320.

It is an arithmetic number, because the mean of its divisors is an integer number (10406320).

Almost surely, 2^20812639 is an apocalyptic number.

20812639 is a deficient number, since it is larger than the sum of its proper divisors (1).

20812639 is an equidigital number, since it uses as much as digits as its factorization.

20812639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 20812639 is about 4562.0871320044. The cubic root of 20812639 is about 275.0694656469.

The spelling of 20812639 in words is "twenty million, eight hundred twelve thousand, six hundred thirty-nine".