661671760 has 20 divisors (see below), whose sum is σ = 1538387028. Its totient is φ = 264668672.

The previous prime is 661671757. The next prime is 661671761. The reversal of 661671760 is 67176166.

It can be written as a sum of positive squares in 2 ways, for example, as 214095424 + 447576336 = 14632^2 + 21156^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661671761) 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, 4135369 + ... + 4135528.

Almost surely, 2^661671760 is an apocalyptic number.

It is an amenable number.

661671760 is an abundant number, since it is smaller than the sum of its proper divisors (876715268).

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

661671760 is a wasteful number, since it uses less digits than its factorization.

661671760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8270910 (or 8270904 counting only the distinct ones).

The product of its (nonzero) digits is 63504, while the sum is 40.

The square root of 661671760 is about 25722.9811647095. The cubic root of 661671760 is about 871.3932667388.

The spelling of 661671760 in words is "six hundred sixty-one million, six hundred seventy-one thousand, seven hundred sixty".