81742457 has 2 divisors, whose sum is σ = 81742458. Its totient is φ = 81742456.

The previous prime is 81742439. The next prime is 81742459. The reversal of 81742457 is 75424718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78570496 + 3171961 = 8864^2 + 1781^2 .

It is a cyclic number.

It is not a de Polignac number, because 81742457 - 2⁸ = 81742201 is a prime.

Together with 81742459, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81742457.

It is not a weakly prime, because it can be changed into another prime (81742459) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40871228 + 40871229.

It is an arithmetic number, because the mean of its divisors is an integer number (40871229).

Almost surely, 2^81742457 is an apocalyptic number.

It is an amenable number.

81742457 is a deficient number, since it is larger than the sum of its proper divisors (1).

81742457 is an equidigital number, since it uses as much as digits as its factorization.

81742457 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62720, while the sum is 38.

The square root of 81742457 is about 9041.1535215370. The cubic root of 81742457 is about 433.9928379119.

The spelling of 81742457 in words is "eighty-one million, seven hundred forty-two thousand, four hundred fifty-seven".