665664261 has 4 divisors (see below), whose sum is σ = 887552352. Its totient is φ = 443776172.

The previous prime is 665664239. The next prime is 665664281. The reversal of 665664261 is 162466566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 665664261 - 2⁷ = 665664133 is a prime.

It is a super-2 number, since 2×665664261² = 886217816745352242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665664211) 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, 110944041 + ... + 110944046.

It is an arithmetic number, because the mean of its divisors is an integer number (221888088).

Almost surely, 2^665664261 is an apocalyptic number.

It is an amenable number.

665664261 is a deficient number, since it is larger than the sum of its proper divisors (221888091).

665664261 is a wasteful number, since it uses less digits than its factorization.

665664261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221888090.

The product of its digits is 311040, while the sum is 42.

The square root of 665664261 is about 25800.4701701345. The cubic root of 665664261 is about 873.1424041016.

The spelling of 665664261 in words is "six hundred sixty-five million, six hundred sixty-four thousand, two hundred sixty-one".