661626331605 has 48 divisors (see below), whose sum is σ = 1176313572720. Its totient is φ = 343898265600.

The previous prime is 661626331573. The next prime is 661626331627. The reversal of 661626331605 is 506133626166.

661626331605 is a `hidden beast` number, since 6 + 6 + 1 + 6 + 2 + 6 + 3 + 31 + 605 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 2149156881 + 659477174724 = 46359^2 + 812082^2 .

It is not a de Polignac number, because 661626331605 - 2⁵ = 661626331573 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 806436 + ... + 1404845.

It is an arithmetic number, because the mean of its divisors is an integer number (24506532765).

Almost surely, 2^661626331605 is an apocalyptic number.

It is an amenable number.

661626331605 is a deficient number, since it is larger than the sum of its proper divisors (514687241115).

661626331605 is a wasteful number, since it uses less digits than its factorization.

661626331605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2211462 (or 2211459 counting only the distinct ones).

The product of its (nonzero) digits is 699840, while the sum is 45.

The spelling of 661626331605 in words is "six hundred sixty-one billion, six hundred twenty-six million, three hundred thirty-one thousand, six hundred five".