20566990621 has 2 divisors, whose sum is σ = 20566990622. Its totient is φ = 20566990620.

The previous prime is 20566990573. The next prime is 20566990627. The reversal of 20566990621 is 12609966502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11714815225 + 8852175396 = 108235^2 + 94086^2 .

It is a cyclic number.

It is not a de Polignac number, because 20566990621 - 2¹⁷ = 20566859549 is a prime.

It is a super-2 number, since 2×20566990621² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20566990627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10283495310 + 10283495311.

It is an arithmetic number, because the mean of its divisors is an integer number (10283495311).

Almost surely, 2^20566990621 is an apocalyptic number.

It is an amenable number.

20566990621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20566990621 is an equidigital number, since it uses as much as digits as its factorization.

20566990621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 349920, while the sum is 46.

The spelling of 20566990621 in words is "twenty billion, five hundred sixty-six million, nine hundred ninety thousand, six hundred twenty-one".