646201978 has 12 divisors (see below), whose sum is σ = 981142938. Its totient is φ = 319201400.

The previous prime is 646201973. The next prime is 646201981. The reversal of 646201978 is 879102646.

It can be written as a sum of positive squares in only one way, i.e., 400120009 + 246081969 = 20003^2 + 15687^2 .

It is a super-2 number, since 2×646201978² = 835153992742224968, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (646201973) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9673 + ... + 37228.

Almost surely, 2^646201978 is an apocalyptic number.

646201978 is a deficient number, since it is larger than the sum of its proper divisors (334940960).

646201978 is an equidigital number, since it uses as much as digits as its factorization.

646201978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47069 (or 46986 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 43.

The square root of 646201978 is about 25420.5031028105. The cubic root of 646201978 is about 864.5486314961.

The spelling of 646201978 in words is "six hundred forty-six million, two hundred one thousand, nine hundred seventy-eight".