640992281 has 2 divisors, whose sum is σ = 640992282. Its totient is φ = 640992280.

The previous prime is 640992263. The next prime is 640992311. The reversal of 640992281 is 182299046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 349129225 + 291863056 = 18685^2 + 17084^2 .

It is a cyclic number.

It is not a de Polignac number, because 640992281 - 2¹⁸ = 640730137 is a prime.

It is a super-2 number, since 2×640992281² = 821742208603165922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640992881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320496140 + 320496141.

It is an arithmetic number, because the mean of its divisors is an integer number (320496141).

Almost surely, 2^640992281 is an apocalyptic number.

It is an amenable number.

640992281 is a deficient number, since it is larger than the sum of its proper divisors (1).

640992281 is an equidigital number, since it uses as much as digits as its factorization.

640992281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62208, while the sum is 41.

The square root of 640992281 is about 25317.8253608006. The cubic root of 640992281 is about 862.2190219949.

The spelling of 640992281 in words is "six hundred forty million, nine hundred ninety-two thousand, two hundred eighty-one".