661551606 has 12 divisors (see below), whose sum is σ = 1433361852. Its totient is φ = 220517196.

The previous prime is 661551589. The next prime is 661551641. The reversal of 661551606 is 606155166.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 18376416 + ... + 18376451.

It is an arithmetic number, because the mean of its divisors is an integer number (119446821).

Almost surely, 2^661551606 is an apocalyptic number.

661551606 is an abundant number, since it is smaller than the sum of its proper divisors (771810246).

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

661551606 is a wasteful number, since it uses less digits than its factorization.

661551606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36752875 (or 36752872 counting only the distinct ones).

The product of its (nonzero) digits is 32400, while the sum is 36.

The square root of 661551606 is about 25720.6455206707. The cubic root of 661551606 is about 871.3405176613.

It can be divided in two parts, 66155160 and 6, that added together give a palindrome (66155166).

The spelling of 661551606 in words is "six hundred sixty-one million, five hundred fifty-one thousand, six hundred six".