997991213 has 2 divisors, whose sum is σ = 997991214. Its totient is φ = 997991212.

The previous prime is 997991191. The next prime is 997991221. The reversal of 997991213 is 312199799.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 533933449 + 464057764 = 23107^2 + 21542^2 .

It is an emirp because it is prime and its reverse (312199799) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 997991213 - 2¹⁸ = 997729069 is a prime.

It is a super-2 number, since 2×997991213² = 1991972922450422738, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (997991233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 498995606 + 498995607.

It is an arithmetic number, because the mean of its divisors is an integer number (498995607).

Almost surely, 2^997991213 is an apocalyptic number.

It is an amenable number.

997991213 is a deficient number, since it is larger than the sum of its proper divisors (1).

997991213 is an equidigital number, since it uses as much as digits as its factorization.

997991213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 275562, while the sum is 50.

The square root of 997991213 is about 31590.9989237441. The cubic root of 997991213 is about 999.3299554739.

The spelling of 997991213 in words is "nine hundred ninety-seven million, nine hundred ninety-one thousand, two hundred thirteen".