81194381 has 2 divisors, whose sum is σ = 81194382. Its totient is φ = 81194380.

The previous prime is 81194371. The next prime is 81194389. The reversal of 81194381 is 18349118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53421481 + 27772900 = 7309^2 + 5270^2 .

It is a cyclic number.

It is not a de Polignac number, because 81194381 - 2¹⁴ = 81177997 is a prime.

It is a super-2 number, since 2×81194381² = 13185055011946322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81194389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40597190 + 40597191.

It is an arithmetic number, because the mean of its divisors is an integer number (40597191).

Almost surely, 2^81194381 is an apocalyptic number.

It is an amenable number.

81194381 is a deficient number, since it is larger than the sum of its proper divisors (1).

81194381 is an equidigital number, since it uses as much as digits as its factorization.

81194381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 35.

The square root of 81194381 is about 9010.7924734731. The cubic root of 81194381 is about 433.0207006693.

The spelling of 81194381 in words is "eighty-one million, one hundred ninety-four thousand, three hundred eighty-one".