661355825 has 12 divisors (see below), whose sum is σ = 883164828. Its totient is φ = 488385600.

The previous prime is 661355809. The next prime is 661355831. The reversal of 661355825 is 528553166.

It can be written as a sum of positive squares in 6 ways, for example, as 44528929 + 616826896 = 6673^2 + 24836^2 .

It is not a de Polignac number, because 661355825 - 2⁴ = 661355809 is a prime.

It is a super-2 number, since 2×661355825² = 874783054522861250, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1017146 + ... + 1017795.

It is an arithmetic number, because the mean of its divisors is an integer number (73597069).

Almost surely, 2^661355825 is an apocalyptic number.

661355825 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

661355825 is a deficient number, since it is larger than the sum of its proper divisors (221809003).

661355825 is a wasteful number, since it uses less digits than its factorization.

661355825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2034964 (or 2034959 counting only the distinct ones).

The product of its digits is 216000, while the sum is 41.

The square root of 661355825 is about 25716.8393275690. The cubic root of 661355825 is about 871.2545537206.

The spelling of 661355825 in words is "six hundred sixty-one million, three hundred fifty-five thousand, eight hundred twenty-five".