20997862621 has 2 divisors, whose sum is σ = 20997862622. Its totient is φ = 20997862620.

The previous prime is 20997862601. The next prime is 20997862657. The reversal of 20997862621 is 12626879902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17254136025 + 3743726596 = 131355^2 + 61186^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20997862621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20997862601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10498931310 + 10498931311.

It is an arithmetic number, because the mean of its divisors is an integer number (10498931311).

Almost surely, 2^20997862621 is an apocalyptic number.

It is an amenable number.

20997862621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20997862621 is an equidigital number, since it uses as much as digits as its factorization.

20997862621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1306368, while the sum is 52.

The spelling of 20997862621 in words is "twenty billion, nine hundred ninety-seven million, eight hundred sixty-two thousand, six hundred twenty-one".