991887893 has 2 divisors, whose sum is σ = 991887894. Its totient is φ = 991887892.

The previous prime is 991887889. The next prime is 991887943. The reversal of 991887893 is 398788199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 769341169 + 222546724 = 27737^2 + 14918^2 .

It is an emirp because it is prime and its reverse (398788199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991887893 - 2² = 991887889 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991887833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495943946 + 495943947.

It is an arithmetic number, because the mean of its divisors is an integer number (495943947).

Almost surely, 2^991887893 is an apocalyptic number.

It is an amenable number.

991887893 is a deficient number, since it is larger than the sum of its proper divisors (1).

991887893 is an equidigital number, since it uses as much as digits as its factorization.

991887893 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7838208, while the sum is 62.

The square root of 991887893 is about 31494.2517453582. The cubic root of 991887893 is about 997.2886193929.

The spelling of 991887893 in words is "nine hundred ninety-one million, eight hundred eighty-seven thousand, eight hundred ninety-three".