397786021 has 2 divisors, whose sum is σ = 397786022. Its totient is φ = 397786020.

The previous prime is 397786007. The next prime is 397786027. The reversal of 397786021 is 120687793.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 332661121 + 65124900 = 18239^2 + 8070^2 .

It is an emirp because it is prime and its reverse (120687793) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-397786021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (397786027) 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, 198893010 + 198893011.

It is an arithmetic number, because the mean of its divisors is an integer number (198893011).

Almost surely, 2^397786021 is an apocalyptic number.

It is an amenable number.

397786021 is a deficient number, since it is larger than the sum of its proper divisors (1).

397786021 is an equidigital number, since it uses as much as digits as its factorization.

397786021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 127008, while the sum is 43.

The square root of 397786021 is about 19944.5737231960. The cubic root of 397786021 is about 735.4443891989. Note that the first 3 decimals are identical.

It can be divided in two parts, 3977 and 86021, that added together give a palindrome (89998).

The spelling of 397786021 in words is "three hundred ninety-seven million, seven hundred eighty-six thousand, twenty-one".