997738991 has 2 divisors, whose sum is σ = 997738992. Its totient is φ = 997738990.

The previous prime is 997738981. The next prime is 997739033. The reversal of 997738991 is 199837799.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-997738991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (997738901) 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, 498869495 + 498869496.

It is an arithmetic number, because the mean of its divisors is an integer number (498869496).

Almost surely, 2^997738991 is an apocalyptic number.

997738991 is a deficient number, since it is larger than the sum of its proper divisors (1).

997738991 is an equidigital number, since it uses as much as digits as its factorization.

997738991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7715736, while the sum is 62.

The square root of 997738991 is about 31587.0066799626. The cubic root of 997738991 is about 999.2457616008.

The spelling of 997738991 in words is "nine hundred ninety-seven million, seven hundred thirty-eight thousand, nine hundred ninety-one".