81357251 has 2 divisors, whose sum is σ = 81357252. Its totient is φ = 81357250.

The previous prime is 81357193. The next prime is 81357253. The reversal of 81357251 is 15275318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81357251 - 2²² = 77162947 is a prime.

Together with 81357253, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81357253) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40678625 + 40678626.

It is an arithmetic number, because the mean of its divisors is an integer number (40678626).

Almost surely, 2^81357251 is an apocalyptic number.

81357251 is a deficient number, since it is larger than the sum of its proper divisors (1).

81357251 is an equidigital number, since it uses as much as digits as its factorization.

81357251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 32.

The square root of 81357251 is about 9019.8254417699. The cubic root of 81357251 is about 433.3100432585.

The spelling of 81357251 in words is "eighty-one million, three hundred fifty-seven thousand, two hundred fifty-one".