661642815 has 16 divisors (see below), whose sum is σ = 1076572800. Its totient is φ = 346894752.

The previous prime is 661642799. The next prime is 661642847. The reversal of 661642815 is 518246166.

It is a happy number.

It is not a de Polignac number, because 661642815 - 2⁴ = 661642799 is a prime.

It is a super-2 number, since 2×661642815² = 875542429282248450, which contains 22 as substring.

It is a congruent number.

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, 372925 + ... + 374694.

It is an arithmetic number, because the mean of its divisors is an integer number (67285800).

Almost surely, 2^661642815 is an apocalyptic number.

661642815 is a deficient number, since it is larger than the sum of its proper divisors (414929985).

661642815 is a wasteful number, since it uses less digits than its factorization.

661642815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 747686.

The product of its digits is 69120, while the sum is 39.

The square root of 661642815 is about 25722.4185293685. The cubic root of 661642815 is about 871.3805601132.

The spelling of 661642815 in words is "six hundred sixty-one million, six hundred forty-two thousand, eight hundred fifteen".