20644406257 has 2 divisors, whose sum is σ = 20644406258. Its totient is φ = 20644406256.

The previous prime is 20644406239. The next prime is 20644406273. The reversal of 20644406257 is 75260444602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14009326321 + 6635079936 = 118361^2 + 81456^2 .

It is a cyclic number.

It is not a de Polignac number, because 20644406257 - 2¹⁹ = 20643881969 is a prime.

It is not a weakly prime, because it can be changed into another prime (20644406207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10322203128 + 10322203129.

It is an arithmetic number, because the mean of its divisors is an integer number (10322203129).

Almost surely, 2^20644406257 is an apocalyptic number.

It is an amenable number.

20644406257 is a deficient number, since it is larger than the sum of its proper divisors (1).

20644406257 is an equidigital number, since it uses as much as digits as its factorization.

20644406257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 322560, while the sum is 40.

The spelling of 20644406257 in words is "twenty billion, six hundred forty-four million, four hundred six thousand, two hundred fifty-seven".