997399981 has 2 divisors, whose sum is σ = 997399982. Its totient is φ = 997399980.

The previous prime is 997399973. The next prime is 997400011. The reversal of 997399981 is 189993799.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 563302756 + 434097225 = 23734^2 + 20835^2 .

It is a cyclic number.

It is not a de Polignac number, because 997399981 - 2³ = 997399973 is a prime.

It is a super-2 number, since 2×997399981² = 1989613444197600722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (997399901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 498699990 + 498699991.

It is an arithmetic number, because the mean of its divisors is an integer number (498699991).

Almost surely, 2^997399981 is an apocalyptic number.

It is an amenable number.

997399981 is a deficient number, since it is larger than the sum of its proper divisors (1).

997399981 is an equidigital number, since it uses as much as digits as its factorization.

997399981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9920232, while the sum is 64.

The square root of 997399981 is about 31581.6399352535. The cubic root of 997399981 is about 999.1325747911.

The spelling of 997399981 in words is "nine hundred ninety-seven million, three hundred ninety-nine thousand, nine hundred eighty-one".