661644923 has 4 divisors (see below), whose sum is σ = 696468360. Its totient is φ = 626821488.

The previous prime is 661644877. The next prime is 661644937. The reversal of 661644923 is 329446166.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 661644923 - 2⁶ = 661644859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661644983) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17411690 + ... + 17411727.

It is an arithmetic number, because the mean of its divisors is an integer number (174117090).

Almost surely, 2^661644923 is an apocalyptic number.

661644923 is a deficient number, since it is larger than the sum of its proper divisors (34823437).

661644923 is a wasteful number, since it uses less digits than its factorization.

661644923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34823436.

The product of its digits is 186624, while the sum is 41.

The square root of 661644923 is about 25722.4595052650. The cubic root of 661644923 is about 871.3814855210.

The spelling of 661644923 in words is "six hundred sixty-one million, six hundred forty-four thousand, nine hundred twenty-three".