991887919 has 16 divisors (see below), whose sum is σ = 1089728640. Its totient is φ = 895353760.

The previous prime is 991887893. The next prime is 991887943. The reversal of 991887919 is 919788199.

It is a cyclic number.

It is not a de Polignac number, because 991887919 - 2¹¹ = 991885871 is a prime.

It is a super-2 number, since 2×991887919² = 1967683287716301122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991887979) 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, 1504812 + ... + 1505470.

It is an arithmetic number, because the mean of its divisors is an integer number (68108040).

Almost surely, 2^991887919 is an apocalyptic number.

991887919 is a deficient number, since it is larger than the sum of its proper divisors (97840721).

991887919 is a wasteful number, since it uses less digits than its factorization.

991887919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1430.

The product of its digits is 2939328, while the sum is 61.

The square root of 991887919 is about 31494.2521581320. The cubic root of 991887919 is about 997.2886281067.

The spelling of 991887919 in words is "nine hundred ninety-one million, eight hundred eighty-seven thousand, nine hundred nineteen".