661966291 has 16 divisors (see below), whose sum is σ = 766320640. Its totient is φ = 560105280.

The previous prime is 661966259. The next prime is 661966321. The reversal of 661966291 is 192669166.

It is not a de Polignac number, because 661966291 - 2⁵ = 661966259 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661966241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 185815 + ... + 189343.

It is an arithmetic number, because the mean of its divisors is an integer number (47895040).

Almost surely, 2^661966291 is an apocalyptic number.

661966291 is a deficient number, since it is larger than the sum of its proper divisors (104354349).

661966291 is a wasteful number, since it uses less digits than its factorization.

661966291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3874.

The product of its digits is 209952, while the sum is 46.

The square root of 661966291 is about 25728.7055834529. The cubic root of 661966291 is about 871.5225424481.

The spelling of 661966291 in words is "six hundred sixty-one million, nine hundred sixty-six thousand, two hundred ninety-one".