661988611 has 4 divisors (see below), whose sum is σ = 662342800. Its totient is φ = 661634424.

The previous prime is 661988543. The next prime is 661988627. The reversal of 661988611 is 116889166.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 661988611 - 2⁹ = 661988099 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661988641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 174276 + ... + 178033.

It is an arithmetic number, because the mean of its divisors is an integer number (165585700).

Almost surely, 2^661988611 is an apocalyptic number.

661988611 is a deficient number, since it is larger than the sum of its proper divisors (354189).

661988611 is a wasteful number, since it uses less digits than its factorization.

661988611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354188.

The product of its digits is 124416, while the sum is 46.

The square root of 661988611 is about 25729.1393365577. The cubic root of 661988611 is about 871.5323375916.

The spelling of 661988611 in words is "six hundred sixty-one million, nine hundred eighty-eight thousand, six hundred eleven".