991270018421 has 2 divisors, whose sum is σ = 991270018422. Its totient is φ = 991270018420.

The previous prime is 991270018399. The next prime is 991270018429. The reversal of 991270018421 is 124810072199.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 972272909521 + 18997108900 = 986039^2 + 137830^2 .

It is an emirp because it is prime and its reverse (124810072199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991270018421 - 2¹⁸ = 991269756277 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991270018429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495635009210 + 495635009211.

It is an arithmetic number, because the mean of its divisors is an integer number (495635009211).

Almost surely, 2^991270018421 is an apocalyptic number.

It is an amenable number.

991270018421 is a deficient number, since it is larger than the sum of its proper divisors (1).

991270018421 is an equidigital number, since it uses as much as digits as its factorization.

991270018421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72576, while the sum is 44.

The spelling of 991270018421 in words is "nine hundred ninety-one billion, two hundred seventy million, eighteen thousand, four hundred twenty-one".