645558878 has 4 divisors (see below), whose sum is σ = 968338320. Its totient is φ = 322779438.

The previous prime is 645558847. The next prime is 645558923. The reversal of 645558878 is 878855546.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 161389718 + ... + 161389721.

It is an arithmetic number, because the mean of its divisors is an integer number (242084580).

Almost surely, 2^645558878 is an apocalyptic number.

645558878 is a deficient number, since it is larger than the sum of its proper divisors (322779442).

645558878 is a wasteful number, since it uses less digits than its factorization.

645558878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322779441.

The product of its digits is 10752000, while the sum is 56.

The square root of 645558878 is about 25407.8507158713. The cubic root of 645558878 is about 864.2617367961.

The spelling of 645558878 in words is "six hundred forty-five million, five hundred fifty-eight thousand, eight hundred seventy-eight".