661831566 has 16 divisors (see below), whose sum is σ = 1443996288. Its totient is φ = 200555000.

The previous prime is 661831559. The next prime is 661831567. The reversal of 661831566 is 665138166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661831567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5013810 + ... + 5013941.

It is an arithmetic number, because the mean of its divisors is an integer number (90249768).

Almost surely, 2^661831566 is an apocalyptic number.

661831566 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

661831566 is an abundant number, since it is smaller than the sum of its proper divisors (782164722).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661831566 is a wasteful number, since it uses less digits than its factorization.

661831566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10027767.

The product of its digits is 155520, while the sum is 42.

The square root of 661831566 is about 25726.0872656531. The cubic root of 661831566 is about 871.4634136361.

The spelling of 661831566 in words is "six hundred sixty-one million, eight hundred thirty-one thousand, five hundred sixty-six".