661891898 has 8 divisors (see below), whose sum is σ = 995339892. Its totient is φ = 330111936.

The previous prime is 661891877. The next prime is 661891903. The reversal of 661891898 is 898198166.

It can be written as a sum of positive squares in 2 ways, for example, as 660644209 + 1247689 = 25703^2 + 1117^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 416015 + ... + 417602.

Almost surely, 2^661891898 is an apocalyptic number.

661891898 is a deficient number, since it is larger than the sum of its proper divisors (333447994).

661891898 is a wasteful number, since it uses less digits than its factorization.

661891898 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 834016.

The product of its digits is 1492992, while the sum is 56.

The square root of 661891898 is about 25727.2598229971. The cubic root of 661891898 is about 871.4898934516.

The spelling of 661891898 in words is "six hundred sixty-one million, eight hundred ninety-one thousand, eight hundred ninety-eight".