661693638 has 16 divisors (see below), whose sum is σ = 1369021680. Its totient is φ = 212958816.

The previous prime is 661693621. The next prime is 661693663. The reversal of 661693638 is 836396166.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1901245 + ... + 1901592.

It is an arithmetic number, because the mean of its divisors is an integer number (85563855).

Almost surely, 2^661693638 is an apocalyptic number.

661693638 is an abundant number, since it is smaller than the sum of its proper divisors (707328042).

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

661693638 is a wasteful number, since it uses less digits than its factorization.

661693638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3802871.

The product of its digits is 839808, while the sum is 48.

The square root of 661693638 is about 25723.4064229448. The cubic root of 661693638 is about 871.4028707615.

The spelling of 661693638 in words is "six hundred sixty-one million, six hundred ninety-three thousand, six hundred thirty-eight".