991745281 has 2 divisors, whose sum is σ = 991745282. Its totient is φ = 991745280.

The previous prime is 991745239. The next prime is 991745309. The reversal of 991745281 is 182547199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 985394881 + 6350400 = 31391^2 + 2520^2 .

It is a cyclic number.

It is not a de Polignac number, because 991745281 - 2⁹ = 991744769 is a prime.

It is a super-2 number, since 2×991745281² = 1967117404771537922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (991745221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495872640 + 495872641.

It is an arithmetic number, because the mean of its divisors is an integer number (495872641).

Almost surely, 2^991745281 is an apocalyptic number.

It is an amenable number.

991745281 is a deficient number, since it is larger than the sum of its proper divisors (1).

991745281 is an equidigital number, since it uses as much as digits as its factorization.

991745281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 181440, while the sum is 46.

The square root of 991745281 is about 31491.9875682689. The cubic root of 991745281 is about 997.2408209328.

The spelling of 991745281 in words is "nine hundred ninety-one million, seven hundred forty-five thousand, two hundred eighty-one".