645079931 has 4 divisors (see below), whose sum is σ = 645515232. Its totient is φ = 644644632.

The previous prime is 645079891. The next prime is 645079969. The reversal of 645079931 is 139970546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 139970546 = 2 ⋅69985273.

It is a cyclic number.

It is not a de Polignac number, because 645079931 - 2²² = 640885627 is a prime.

It is a super-2 number, since 2×645079931² = 832256234757929522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645079531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 215420 + ... + 218393.

It is an arithmetic number, because the mean of its divisors is an integer number (161378808).

Almost surely, 2^645079931 is an apocalyptic number.

645079931 is a deficient number, since it is larger than the sum of its proper divisors (435301).

645079931 is a wasteful number, since it uses less digits than its factorization.

645079931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 435300.

The product of its (nonzero) digits is 204120, while the sum is 44.

The square root of 645079931 is about 25398.4237896764. The cubic root of 645079931 is about 864.0479489243.

The spelling of 645079931 in words is "six hundred forty-five million, seventy-nine thousand, nine hundred thirty-one".