20657440261 has 2 divisors, whose sum is σ = 20657440262. Its totient is φ = 20657440260.

The previous prime is 20657440229. The next prime is 20657440267. The reversal of 20657440261 is 16204475602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15185879361 + 5471560900 = 123231^2 + 73970^2 .

It is a cyclic number.

It is not a de Polignac number, because 20657440261 - 2⁵ = 20657440229 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20657440261.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20657440267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10328720130 + 10328720131.

It is an arithmetic number, because the mean of its divisors is an integer number (10328720131).

Almost surely, 2^20657440261 is an apocalyptic number.

It is an amenable number.

20657440261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20657440261 is an equidigital number, since it uses as much as digits as its factorization.

20657440261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 80640, while the sum is 37.

The spelling of 20657440261 in words is "twenty billion, six hundred fifty-seven million, four hundred forty thousand, two hundred sixty-one".