661634637 has 4 divisors (see below), whose sum is σ = 882179520. Its totient is φ = 441089756.

The previous prime is 661634627. The next prime is 661634639. The reversal of 661634637 is 736436166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 661634637 - 2¹¹ = 661632589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661634639) 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, 110272437 + ... + 110272442.

It is an arithmetic number, because the mean of its divisors is an integer number (220544880).

Almost surely, 2^661634637 is an apocalyptic number.

It is an amenable number.

661634637 is a deficient number, since it is larger than the sum of its proper divisors (220544883).

661634637 is a wasteful number, since it uses less digits than its factorization.

661634637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220544882.

The product of its digits is 326592, while the sum is 42.

The square root of 661634637 is about 25722.2595624879. The cubic root of 661634637 is about 871.3769699689.

The spelling of 661634637 in words is "six hundred sixty-one million, six hundred thirty-four thousand, six hundred thirty-seven".