991619 has 2 divisors, whose sum is σ = 991620. Its totient is φ = 991618.

The previous prime is 991607. The next prime is 991621. The reversal of 991619 is 916199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991619 - 2⁴ = 991603 is a prime.

It is a super-2 number, since 2×991619² = 1966616482322, which contains 22 as substring.

Together with 991621, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is equal to p₇₇₈₉₄ and since 991619 and 77894 have the same sum of digits, it is a Honaker prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991619.

It is not a weakly prime, because it can be changed into another prime (961619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495809 + 495810.

It is an arithmetic number, because the mean of its divisors is an integer number (495810).

2⁹⁹¹⁶¹⁹ is an apocalyptic number.

991619 is a deficient number, since it is larger than the sum of its proper divisors (1).

991619 is an equidigital number, since it uses as much as digits as its factorization.

991619 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4374, while the sum is 35.

The square root of 991619 is about 995.8006828678. The cubic root of 991619 is about 99.7198492217.

The spelling of 991619 in words is "nine hundred ninety-one thousand, six hundred nineteen".