997860821 has 2 divisors, whose sum is σ = 997860822. Its totient is φ = 997860820.

The previous prime is 997860817. The next prime is 997860823. The reversal of 997860821 is 128068799.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 881436721 + 116424100 = 29689^2 + 10790^2 .

It is a cyclic number.

It is not a de Polignac number, because 997860821 - 2² = 997860817 is a prime.

Together with 997860823, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 997860821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (997860823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 498930410 + 498930411.

It is an arithmetic number, because the mean of its divisors is an integer number (498930411).

Almost surely, 2^997860821 is an apocalyptic number.

It is an amenable number.

997860821 is a deficient number, since it is larger than the sum of its proper divisors (1).

997860821 is an equidigital number, since it uses as much as digits as its factorization.

997860821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 435456, while the sum is 50.

The square root of 997860821 is about 31588.9351039252. The cubic root of 997860821 is about 999.2864312741.

The spelling of 997860821 in words is "nine hundred ninety-seven million, eight hundred sixty thousand, eight hundred twenty-one".