661568136 has 64 divisors (see below), whose sum is σ = 1733339520. Its totient is φ = 210017280.

The previous prime is 661568129. The next prime is 661568147. The reversal of 661568136 is 631865166.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 130546 + ... + 135518.

It is an arithmetic number, because the mean of its divisors is an integer number (27083430).

Almost surely, 2^661568136 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661568136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (866669760).

661568136 is an abundant number, since it is smaller than the sum of its proper divisors (1071771384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661568136 is a wasteful number, since it uses less digits than its factorization.

661568136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5246 (or 5242 counting only the distinct ones).

The product of its digits is 155520, while the sum is 42.

The square root of 661568136 is about 25720.9668558552. The cubic root of 661568136 is about 871.3477749126.

The spelling of 661568136 in words is "six hundred sixty-one million, five hundred sixty-eight thousand, one hundred thirty-six".