90172991 has 2 divisors, whose sum is σ = 90172992. Its totient is φ = 90172990.

The previous prime is 90172967. The next prime is 90172997. The reversal of 90172991 is 19927109.

It is a strong prime.

It is an emirp because it is prime and its reverse (19927109) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 90172991 - 2²⁶ = 23064127 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (90172997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45086495 + 45086496.

It is an arithmetic number, because the mean of its divisors is an integer number (45086496).

Almost surely, 2^90172991 is an apocalyptic number.

90172991 is a deficient number, since it is larger than the sum of its proper divisors (1).

90172991 is an equidigital number, since it uses as much as digits as its factorization.

90172991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 90172991 is about 9495.9460297540. The cubic root of 90172991 is about 448.4274178092.

The spelling of 90172991 in words is "ninety million, one hundred seventy-two thousand, nine hundred ninety-one".