661633861 has 8 divisors (see below), whose sum is σ = 756959040. Its totient is φ = 566510208.

The previous prime is 661633781. The next prime is 661633867. The reversal of 661633861 is 168336166.

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

It is a cyclic number.

It is not a de Polignac number, because 661633861 - 2²³ = 653245253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661633867) 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, 43276 + ... + 56533.

It is an arithmetic number, because the mean of its divisors is an integer number (94619880).

Almost surely, 2^661633861 is an apocalyptic number.

It is an amenable number.

661633861 is a deficient number, since it is larger than the sum of its proper divisors (95325179).

661633861 is an equidigital number, since it uses as much as digits as its factorization.

661633861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100763.

The product of its digits is 93312, while the sum is 40.

The square root of 661633861 is about 25722.2444782721. The cubic root of 661633861 is about 871.3766293031.

The spelling of 661633861 in words is "six hundred sixty-one million, six hundred thirty-three thousand, eight hundred sixty-one".