81751237 has 2 divisors, whose sum is σ = 81751238. Its totient is φ = 81751236.

The previous prime is 81751231. The next prime is 81751259. The reversal of 81751237 is 73215718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 79816356 + 1934881 = 8934^2 + 1391^2 .

It is a cyclic number.

It is not a de Polignac number, because 81751237 - 2¹¹ = 81749189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81751231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40875618 + 40875619.

It is an arithmetic number, because the mean of its divisors is an integer number (40875619).

Almost surely, 2^81751237 is an apocalyptic number.

It is an amenable number.

81751237 is a deficient number, since it is larger than the sum of its proper divisors (1).

81751237 is an equidigital number, since it uses as much as digits as its factorization.

81751237 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11760, while the sum is 34.

The square root of 81751237 is about 9041.6390660101. The cubic root of 81751237 is about 434.0083758214.

The spelling of 81751237 in words is "eighty-one million, seven hundred fifty-one thousand, two hundred thirty-seven".