640661023 has 2 divisors, whose sum is σ = 640661024. Its totient is φ = 640661022.

The previous prime is 640661017. The next prime is 640661027. The reversal of 640661023 is 320166046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640661023 - 2²⁹ = 103790111 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640660982 and 640661000.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640661027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320330511 + 320330512.

It is an arithmetic number, because the mean of its divisors is an integer number (320330512).

Almost surely, 2^640661023 is an apocalyptic number.

640661023 is a deficient number, since it is larger than the sum of its proper divisors (1).

640661023 is an equidigital number, since it uses as much as digits as its factorization.

640661023 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 28.

The square root of 640661023 is about 25311.2825238074. The cubic root of 640661023 is about 862.0704678585.

The spelling of 640661023 in words is "six hundred forty million, six hundred sixty-one thousand, twenty-three".