991901899 has 2 divisors, whose sum is σ = 991901900. Its totient is φ = 991901898.

The previous prime is 991901893. The next prime is 991901951. The reversal of 991901899 is 998109199.

It is a weak prime.

It is an emirp because it is prime and its reverse (998109199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991901899 - 2²⁹ = 455030987 is a prime.

It is a super-3 number, since 3×991901899³ (a number of 28 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (991901893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495950949 + 495950950.

It is an arithmetic number, because the mean of its divisors is an integer number (495950950).

Almost surely, 2^991901899 is an apocalyptic number.

991901899 is a deficient number, since it is larger than the sum of its proper divisors (1).

991901899 is an equidigital number, since it uses as much as digits as its factorization.

991901899 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 472392, while the sum is 55.

The square root of 991901899 is about 31494.4741026104. The cubic root of 991901899 is about 997.2933134578.

The spelling of 991901899 in words is "nine hundred ninety-one million, nine hundred one thousand, eight hundred ninety-nine".