661958779 has 8 divisors (see below), whose sum is σ = 683798528. Its totient is φ = 640149480.

The previous prime is 661958743. The next prime is 661958807. The reversal of 661958779 is 977859166.

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

It is a cyclic number.

It is not a de Polignac number, because 661958779 - 2²³ = 653570171 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661953779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41764 + ... + 55390.

It is an arithmetic number, because the mean of its divisors is an integer number (85474816).

Almost surely, 2^661958779 is an apocalyptic number.

661958779 is a deficient number, since it is larger than the sum of its proper divisors (21839749).

661958779 is a wasteful number, since it uses less digits than its factorization.

661958779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15225.

The product of its digits is 5715360, while the sum is 58.

The square root of 661958779 is about 25728.5595982364. The cubic root of 661958779 is about 871.5192457535.

The spelling of 661958779 in words is "six hundred sixty-one million, nine hundred fifty-eight thousand, seven hundred seventy-nine".