661511806 has 4 divisors (see below), whose sum is σ = 992267712. Its totient is φ = 330755902.

The previous prime is 661511783. The next prime is 661511833. The reversal of 661511806 is 608115166.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 165377950 + ... + 165377953.

It is an arithmetic number, because the mean of its divisors is an integer number (248066928).

Almost surely, 2^661511806 is an apocalyptic number.

661511806 is a deficient number, since it is larger than the sum of its proper divisors (330755906).

661511806 is a wasteful number, since it uses less digits than its factorization.

661511806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 330755905.

The product of its (nonzero) digits is 8640, while the sum is 34.

The square root of 661511806 is about 25719.8718115001. The cubic root of 661511806 is about 871.3230435657.

The spelling of 661511806 in words is "six hundred sixty-one million, five hundred eleven thousand, eight hundred six".