661766864 has 20 divisors (see below), whose sum is σ = 1398734880. Its totient is φ = 300803040.

The previous prime is 661766849. The next prime is 661766869. The reversal of 661766864 is 468667166.

It is a happy number.

It is a super-3 number, since 3×661766864³ (a number of 27 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661766869) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1879844 + ... + 1880195.

It is an arithmetic number, because the mean of its divisors is an integer number (69936744).

Almost surely, 2^661766864 is an apocalyptic number.

It is an amenable number.

661766864 is an abundant number, since it is smaller than the sum of its proper divisors (736968016).

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

661766864 is a wasteful number, since it uses less digits than its factorization.

661766864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3760058 (or 3760052 counting only the distinct ones).

The product of its digits is 1741824, while the sum is 50.

The square root of 661766864 is about 25724.8297176094. The cubic root of 661766864 is about 871.4350140320.

The spelling of 661766864 in words is "six hundred sixty-one million, seven hundred sixty-six thousand, eight hundred sixty-four".