991651679 has 4 divisors (see below), whose sum is σ = 991757784. Its totient is φ = 991545576.

The previous prime is 991651669. The next prime is 991651691. The reversal of 991651679 is 976156199.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 991651679 - 2⁴ = 991651663 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991651679.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991651649) 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, 37517 + ... + 58230.

It is an arithmetic number, because the mean of its divisors is an integer number (247939446).

Almost surely, 2^991651679 is an apocalyptic number.

991651679 is a deficient number, since it is larger than the sum of its proper divisors (106105).

991651679 is a wasteful number, since it uses less digits than its factorization.

991651679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106104.

The product of its digits is 918540, while the sum is 53.

The square root of 991651679 is about 31490.5014091551. The cubic root of 991651679 is about 997.2094463874.

The spelling of 991651679 in words is "nine hundred ninety-one million, six hundred fifty-one thousand, six hundred seventy-nine".