645319978 has 8 divisors (see below), whose sum is σ = 969839460. Its totient is φ = 322040160.

The previous prime is 645319973. The next prime is 645320041. The reversal of 645319978 is 879913546.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 645312409 + 7569 = 25403^2 + 87^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (645319973) 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, 308613 + ... + 310696.

Almost surely, 2^645319978 is an apocalyptic number.

645319978 is a deficient number, since it is larger than the sum of its proper divisors (324519482).

645319978 is a wasteful number, since it uses less digits than its factorization.

645319978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 619832.

The product of its digits is 1632960, while the sum is 52.

The square root of 645319978 is about 25403.1489780303. The cubic root of 645319978 is about 864.1551120762.

The spelling of 645319978 in words is "six hundred forty-five million, three hundred nineteen thousand, nine hundred seventy-eight".