991947979 has 8 divisors (see below), whose sum is σ = 1129174272. Its totient is φ = 862563240.

The previous prime is 991947961. The next prime is 991947997. The reversal of 991947979 is 979749199.

It is an interprime number because it is at equal distance from previous prime (991947961) and next prime (991947997).

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

It is not a de Polignac number, because 991947979 - 2¹⁹ = 991423691 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 991947979.

It is not an unprimeable number, because it can be changed into a prime (991947959) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1960119 + ... + 1960624.

It is an arithmetic number, because the mean of its divisors is an integer number (141146784).

Almost surely, 2^991947979 is an apocalyptic number.

991947979 is a deficient number, since it is larger than the sum of its proper divisors (137226293).

991947979 is a wasteful number, since it uses less digits than its factorization.

991947979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3920777.

The product of its digits is 11573604, while the sum is 64.

The square root of 991947979 is about 31495.2056510193. The cubic root of 991947979 is about 997.3087567069.

The spelling of 991947979 in words is "nine hundred ninety-one million, nine hundred forty-seven thousand, nine hundred seventy-nine".