661631693 has 4 divisors (see below), whose sum is σ = 664471548. Its totient is φ = 658791840.

The previous prime is 661631689. The next prime is 661631713. The reversal of 661631693 is 396136166.

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

It can be written as a sum of positive squares in 2 ways, for example, as 74684164 + 586947529 = 8642^2 + 24227^2 .

It is a cyclic number.

It is not a de Polignac number, because 661631693 - 2² = 661631689 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 661631693.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661631603) 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 3 ways as a sum of consecutive naturals, for example, 1419578 + ... + 1420043.

It is an arithmetic number, because the mean of its divisors is an integer number (166117887).

Almost surely, 2^661631693 is an apocalyptic number.

It is an amenable number.

661631693 is a deficient number, since it is larger than the sum of its proper divisors (2839855).

661631693 is a wasteful number, since it uses less digits than its factorization.

661631693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2839854.

The product of its digits is 104976, while the sum is 41.

The square root of 661631693 is about 25722.2023357255. The cubic root of 661631693 is about 871.3756775448.

The spelling of 661631693 in words is "six hundred sixty-one million, six hundred thirty-one thousand, six hundred ninety-three".