397687891 has 2 divisors, whose sum is σ = 397687892. Its totient is φ = 397687890.

The previous prime is 397687819. The next prime is 397687897. The reversal of 397687891 is 198786793.

Together with previous prime (397687819) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 397687891 - 2⁹ = 397687379 is a prime.

It is not a weakly prime, because it can be changed into another prime (397687897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 198843945 + 198843946.

It is an arithmetic number, because the mean of its divisors is an integer number (198843946).

Almost surely, 2^397687891 is an apocalyptic number.

397687891 is the 12613-rd centered pentagonal number.

397687891 is a deficient number, since it is larger than the sum of its proper divisors (1).

397687891 is an equidigital number, since it uses as much as digits as its factorization.

397687891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4572288, while the sum is 58.

The square root of 397687891 is about 19942.1135038391. The cubic root of 397687891 is about 735.3839085306.

The spelling of 397687891 in words is "three hundred ninety-seven million, six hundred eighty-seven thousand, eight hundred ninety-one".