661861885 has 8 divisors (see below), whose sum is σ = 798267096. Its totient is φ = 526800960.

The previous prime is 661861877. The next prime is 661861913. The reversal of 661861885 is 588168166.

It can be written as a sum of positive squares in 4 ways, for example, as 174953529 + 486908356 = 13227^2 + 22066^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661861885 - 2³ = 661861877 is a prime.

It is a super-2 number, since 2×661861885² = 876122309631506450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 334986 + ... + 336955.

It is an arithmetic number, because the mean of its divisors is an integer number (99783387).

Almost surely, 2^661861885 is an apocalyptic number.

It is an amenable number.

661861885 is a deficient number, since it is larger than the sum of its proper divisors (136405211).

661861885 is a wasteful number, since it uses less digits than its factorization.

661861885 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 672143.

The product of its digits is 552960, while the sum is 49.

The square root of 661861885 is about 25726.6765245727. The cubic root of 661861885 is about 871.4767208969.

The spelling of 661861885 in words is "six hundred sixty-one million, eight hundred sixty-one thousand, eight hundred eighty-five".