661896978 has 16 divisors (see below), whose sum is σ = 1327405440. Its totient is φ = 220030416.

The previous prime is 661896947. The next prime is 661897001. The reversal of 661896978 is 879698166.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 148093 + ... + 152496.

It is an arithmetic number, because the mean of its divisors is an integer number (82962840).

Almost surely, 2^661896978 is an apocalyptic number.

661896978 is an abundant number, since it is smaller than the sum of its proper divisors (665508462).

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

661896978 is a wasteful number, since it uses less digits than its factorization.

661896978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300961.

The product of its digits is 7838208, while the sum is 60.

The square root of 661896978 is about 25727.3585507724. The cubic root of 661896978 is about 871.4921229986.

The spelling of 661896978 in words is "six hundred sixty-one million, eight hundred ninety-six thousand, nine hundred seventy-eight".