661633581 has 32 divisors (see below), whose sum is σ = 1021696000. Its totient is φ = 373045824.

The previous prime is 661633573. The next prime is 661633601. The reversal of 661633581 is 185336166.

It is not a de Polignac number, because 661633581 - 2³ = 661633573 is a prime.

It is a super-2 number, since 2×661633581² = 875517991013767122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661633501) 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 31 ways as a sum of consecutive naturals, for example, 1079031 + ... + 1079643.

It is an arithmetic number, because the mean of its divisors is an integer number (31928000).

Almost surely, 2^661633581 is an apocalyptic number.

It is an amenable number.

661633581 is a deficient number, since it is larger than the sum of its proper divisors (360062419).

661633581 is a wasteful number, since it uses less digits than its factorization.

661633581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1225.

The product of its digits is 77760, while the sum is 39.

The square root of 661633581 is about 25722.2390355117. The cubic root of 661633581 is about 871.3765063824.

The spelling of 661633581 in words is "six hundred sixty-one million, six hundred thirty-three thousand, five hundred eighty-one".