661691583 has 24 divisors (see below), whose sum is σ = 1110229536. Its totient is φ = 371908800.

The previous prime is 661691573. The next prime is 661691599. The reversal of 661691583 is 385196166.

661691583 is a `hidden beast` number, since 6 + 6 + 1 + 69 + 1 + 583 = 666.

It is not a de Polignac number, because 661691583 - 2⁶ = 661691519 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661691533) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 82248 + ... + 89933.

It is an arithmetic number, because the mean of its divisors is an integer number (46259564).

Almost surely, 2^661691583 is an apocalyptic number.

661691583 is a gapful number since it is divisible by the number (63) formed by its first and last digit.

661691583 is a deficient number, since it is larger than the sum of its proper divisors (448537953).

661691583 is a wasteful number, since it uses less digits than its factorization.

661691583 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172255 (or 172252 counting only the distinct ones).

The product of its digits is 233280, while the sum is 45.

The square root of 661691583 is about 25723.3664787485. The cubic root of 661691583 is about 871.4019686649.

The spelling of 661691583 in words is "six hundred sixty-one million, six hundred ninety-one thousand, five hundred eighty-three".