897661981 has 2 divisors, whose sum is σ = 897661982. Its totient is φ = 897661980.

The previous prime is 897661957. The next prime is 897661997. The reversal of 897661981 is 189166798.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 890724025 + 6937956 = 29845^2 + 2634^2 .

It is a cyclic number.

It is not a de Polignac number, because 897661981 - 2¹¹ = 897659933 is a prime.

It is a super-2 number, since 2×897661981² = 1611594064265688722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (897661951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 448830990 + 448830991.

It is an arithmetic number, because the mean of its divisors is an integer number (448830991).

Almost surely, 2^897661981 is an apocalyptic number.

It is an amenable number.

897661981 is a deficient number, since it is larger than the sum of its proper divisors (1).

897661981 is an equidigital number, since it uses as much as digits as its factorization.

897661981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1306368, while the sum is 55.

The square root of 897661981 is about 29961.0076766453. The cubic root of 897661981 is about 964.6526105130.

The spelling of 897661981 in words is "eight hundred ninety-seven million, six hundred sixty-one thousand, nine hundred eighty-one".