661571813 has 16 divisors (see below), whose sum is σ = 819181440. Its totient is φ = 521289216.

The previous prime is 661571797. The next prime is 661571843. The reversal of 661571813 is 318175166.

It is not a de Polignac number, because 661571813 - 2⁴ = 661571797 is a prime.

It is a super-2 number, since 2×661571813² = 875354527512213938, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661571843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 59528 + ... + 69761.

It is an arithmetic number, because the mean of its divisors is an integer number (51198840).

Almost surely, 2^661571813 is an apocalyptic number.

It is an amenable number.

661571813 is a deficient number, since it is larger than the sum of its proper divisors (157609627).

661571813 is a wasteful number, since it uses less digits than its factorization.

661571813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129356.

The product of its digits is 30240, while the sum is 38.

The square root of 661571813 is about 25721.0383344063. The cubic root of 661571813 is about 871.3493892285.

The spelling of 661571813 in words is "six hundred sixty-one million, five hundred seventy-one thousand, eight hundred thirteen".