661564266 has 16 divisors (see below), whose sum is σ = 1443413088. Its totient is φ = 200474000.

The previous prime is 661564247. The next prime is 661564271. The reversal of 661564266 is 662465166.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5011785 + ... + 5011916.

It is an arithmetic number, because the mean of its divisors is an integer number (90213318).

Almost surely, 2^661564266 is an apocalyptic number.

661564266 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

661564266 is an abundant number, since it is smaller than the sum of its proper divisors (781848822).

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

661564266 is a wasteful number, since it uses less digits than its factorization.

661564266 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10023717.

The product of its digits is 311040, while the sum is 42.

The square root of 661564266 is about 25720.8916252917. The cubic root of 661564266 is about 871.3460758573.

The spelling of 661564266 in words is "six hundred sixty-one million, five hundred sixty-four thousand, two hundred sixty-six".