661691265 has 16 divisors (see below), whose sum is σ = 1064829888. Its totient is φ = 350860736.

The previous prime is 661691257. The next prime is 661691351. The reversal of 661691265 is 562196166.

It is a cyclic number.

It is not a de Polignac number, because 661691265 - 2³ = 661691257 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 124899 + ... + 130088.

It is an arithmetic number, because the mean of its divisors is an integer number (66551868).

Almost surely, 2^661691265 is an apocalyptic number.

It is an amenable number.

661691265 is a deficient number, since it is larger than the sum of its proper divisors (403138623).

661691265 is a wasteful number, since it uses less digits than its factorization.

661691265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255168.

The product of its digits is 116640, while the sum is 42.

The square root of 661691265 is about 25723.3602975972. The cubic root of 661691265 is about 871.4018290702.

The spelling of 661691265 in words is "six hundred sixty-one million, six hundred ninety-one thousand, two hundred sixty-five".