20939309761 has 4 divisors (see below), whose sum is σ = 20943688752. Its totient is φ = 20934930772.

The previous prime is 20939309759. The next prime is 20939309777. The reversal of 20939309761 is 16790393902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20939309761 - 2¹ = 20939309759 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20939309161) 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 3 ways as a sum of consecutive naturals, for example, 2182315 + ... + 2191888.

It is an arithmetic number, because the mean of its divisors is an integer number (5235922188).

Almost surely, 2^20939309761 is an apocalyptic number.

It is an amenable number.

20939309761 is a deficient number, since it is larger than the sum of its proper divisors (4378991).

20939309761 is an equidigital number, since it uses as much as digits as its factorization.

20939309761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4378990.

The product of its (nonzero) digits is 551124, while the sum is 49.

The spelling of 20939309761 in words is "twenty billion, nine hundred thirty-nine million, three hundred nine thousand, seven hundred sixty-one".