661981072 has 10 divisors (see below), whose sum is σ = 1282588358. Its totient is φ = 330990528.

The previous prime is 661981049. The next prime is 661981091. The reversal of 661981072 is 270189166.

It can be written as a sum of positive squares in only one way, i.e., 465869056 + 196112016 = 21584^2 + 14004^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20686893 + ... + 20686924.

Almost surely, 2^661981072 is an apocalyptic number.

It is an amenable number.

661981072 is a deficient number, since it is larger than the sum of its proper divisors (620607286).

661981072 is a wasteful number, since it uses less digits than its factorization.

661981072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41373825 (or 41373819 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 661981072 is about 25728.9928291023. The cubic root of 661981072 is about 871.5290291222.

The spelling of 661981072 in words is "six hundred sixty-one million, nine hundred eighty-one thousand, seventy-two".