20921977439 has 16 divisors (see below), whose sum is σ = 23868117504. Its totient is φ = 18153458400.

The previous prime is 20921977387. The next prime is 20921977441. The reversal of 20921977439 is 93477912902.

It is not a de Polignac number, because 20921977439 - 2²⁸ = 20653541983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20921977039) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26942 + ... + 206324.

It is an arithmetic number, because the mean of its divisors is an integer number (1491757344).

Almost surely, 2^20921977439 is an apocalyptic number.

20921977439 is a deficient number, since it is larger than the sum of its proper divisors (2946140065).

20921977439 is a wasteful number, since it uses less digits than its factorization.

20921977439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179878.

The product of its (nonzero) digits is 1714608, while the sum is 53.

The spelling of 20921977439 in words is "twenty billion, nine hundred twenty-one million, nine hundred seventy-seven thousand, four hundred thirty-nine".