661161664 has 14 divisors (see below), whose sum is σ = 1311992804. Its totient is φ = 330580800.

The previous prime is 661161661. The next prime is 661161719. The reversal of 661161664 is 466161166.

It is a super-4 number, since 4×661161664⁴ (a number of 36 digits) contains 4444 as substring.

It is not an unprimeable number, because it can be changed into a prime (661161661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5165262 + ... + 5165389.

Almost surely, 2^661161664 is an apocalyptic number.

661161664 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

661161664 is a deficient number, since it is larger than the sum of its proper divisors (650831140).

661161664 is a wasteful number, since it uses less digits than its factorization.

661161664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10330663 (or 10330653 counting only the distinct ones).

The product of its digits is 31104, while the sum is 37.

The square root of 661161664 is about 25713.0640725682. The cubic root of 661161664 is about 871.1692843360.

It can be divided in two parts, 661161 and 664, that added together give a triangular number (661825 = T₁₁₅₀).

The spelling of 661161664 in words is "six hundred sixty-one million, one hundred sixty-one thousand, six hundred sixty-four".