81858431 has 2 divisors, whose sum is σ = 81858432. Its totient is φ = 81858430.

The previous prime is 81858421. The next prime is 81858461. The reversal of 81858431 is 13485818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81858431 - 2⁶ = 81858367 is a prime.

It is a super-2 number, since 2×81858431² = 13401605451563522, 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 (81858421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40929215 + 40929216.

It is an arithmetic number, because the mean of its divisors is an integer number (40929216).

Almost surely, 2^81858431 is an apocalyptic number.

81858431 is a deficient number, since it is larger than the sum of its proper divisors (1).

81858431 is an equidigital number, since it uses as much as digits as its factorization.

81858431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30720, while the sum is 38.

The square root of 81858431 is about 9047.5649210160. The cubic root of 81858431 is about 434.1979867122.

The spelling of 81858431 in words is "eighty-one million, eight hundred fifty-eight thousand, four hundred thirty-one".