645640715 has 4 divisors (see below), whose sum is σ = 774768864. Its totient is φ = 516512568.

The previous prime is 645640711. The next prime is 645640727. The reversal of 645640715 is 517046546.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 645640715 - 2² = 645640711 is a prime.

It is a super-2 number, since 2×645640715² = 833703865731422450, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645640711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64564067 + ... + 64564076.

It is an arithmetic number, because the mean of its divisors is an integer number (193692216).

Almost surely, 2^645640715 is an apocalyptic number.

645640715 is a deficient number, since it is larger than the sum of its proper divisors (129128149).

645640715 is a wasteful number, since it uses less digits than its factorization.

645640715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129128148.

The product of its (nonzero) digits is 100800, while the sum is 38.

The square root of 645640715 is about 25409.4611316336. The cubic root of 645640715 is about 864.2982558505.

The spelling of 645640715 in words is "six hundred forty-five million, six hundred forty thousand, seven hundred fifteen".