2640380257661 has 2 divisors, whose sum is σ = 2640380257662. Its totient is φ = 2640380257660.

The previous prime is 2640380257609. The next prime is 2640380257667. The reversal of 2640380257661 is 1667520830462.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1343756232025 + 1296624025636 = 1159205^2 + 1138694^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2640380257661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2640380257667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1320190128830 + 1320190128831.

It is an arithmetic number, because the mean of its divisors is an integer number (1320190128831).

Almost surely, 2^{2640380257661} is an apocalyptic number.

It is an amenable number.

2640380257661 is a deficient number, since it is larger than the sum of its proper divisors (1).

2640380257661 is an equidigital number, since it uses as much as digits as its factorization.

2640380257661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2903040, while the sum is 50.

The spelling of 2640380257661 in words is "two trillion, six hundred forty billion, three hundred eighty million, two hundred fifty-seven thousand, six hundred sixty-one".