18971681 has 2 divisors, whose sum is σ = 18971682. Its totient is φ = 18971680.

The previous prime is 18971657. The next prime is 18971717. The reversal of 18971681 is 18617981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18190225 + 781456 = 4265^2 + 884^2 .

It is a cyclic number.

It is not a de Polignac number, because 18971681 - 2¹⁴ = 18955297 is a prime.

It is a super-2 number, since 2×18971681² = 719849359931522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (18971611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9485840 + 9485841.

It is an arithmetic number, because the mean of its divisors is an integer number (9485841).

Almost surely, 2^18971681 is an apocalyptic number.

It is an amenable number.

18971681 is a deficient number, since it is larger than the sum of its proper divisors (1).

18971681 is an equidigital number, since it uses as much as digits as its factorization.

18971681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 41.

The square root of 18971681 is about 4355.6493201359. The cubic root of 18971681 is about 266.7075262043.

The spelling of 18971681 in words is "eighteen million, nine hundred seventy-one thousand, six hundred eighty-one".