891997 has 2 divisors, whose sum is σ = 891998. Its totient is φ = 891996.

The previous prime is 891991. The next prime is 892019. The reversal of 891997 is 799198.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 606841 + 285156 = 779^2 + 534^2 .

891997 is a truncatable prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-891997 is a prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (891991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 445998 + 445999.

It is an arithmetic number, because the mean of its divisors is an integer number (445999).

2⁸⁹¹⁹⁹⁷ is an apocalyptic number.

It is an amenable number.

891997 is a deficient number, since it is larger than the sum of its proper divisors (1).

891997 is an equidigital number, since it uses as much as digits as its factorization.

891997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40824, while the sum is 43.

The square root of 891997 is about 944.4559280348. The cubic root of 891997 is about 96.2619077863.

The spelling of 891997 in words is "eight hundred ninety-one thousand, nine hundred ninety-seven".