661539775 has 12 divisors (see below), whose sum is σ = 883410472. Its totient is φ = 488521440.

The previous prime is 661539773. The next prime is 661539779. The reversal of 661539775 is 577935166.

It is not a de Polignac number, because 661539775 - 2¹ = 661539773 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 (661539773) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1017429 + ... + 1018078.

Almost surely, 2^661539775 is an apocalyptic number.

661539775 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

661539775 is a deficient number, since it is larger than the sum of its proper divisors (221870697).

661539775 is a wasteful number, since it uses less digits than its factorization.

661539775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2035530 (or 2035525 counting only the distinct ones).

The product of its digits is 1190700, while the sum is 49.

The square root of 661539775 is about 25720.4155293028. The cubic root of 661539775 is about 871.3353233620.

The spelling of 661539775 in words is "six hundred sixty-one million, five hundred thirty-nine thousand, seven hundred seventy-five".