646976778 has 32 divisors (see below), whose sum is σ = 1495428480. Its totient is φ = 182772480.

The previous prime is 646976773. The next prime is 646976801. The reversal of 646976778 is 877679646.

It is a super-2 number, since 2×646976778² = 837157902542522568, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (646976773) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82803 + ... + 90278.

It is an arithmetic number, because the mean of its divisors is an integer number (46732140).

Almost surely, 2^646976778 is an apocalyptic number.

646976778 is an abundant number, since it is smaller than the sum of its proper divisors (848451702).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

646976778 is a wasteful number, since it uses less digits than its factorization.

646976778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173182.

The product of its digits is 21337344, while the sum is 60.

The square root of 646976778 is about 25435.7382043455. The cubic root of 646976778 is about 864.8940264663.

The spelling of 646976778 in words is "six hundred forty-six million, nine hundred seventy-six thousand, seven hundred seventy-eight".