81872237 has 2 divisors, whose sum is σ = 81872238. Its totient is φ = 81872236.

The previous prime is 81872213. The next prime is 81872269. The reversal of 81872237 is 73227818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81613156 + 259081 = 9034^2 + 509^2 .

It is a cyclic number.

It is not a de Polignac number, because 81872237 - 2¹⁰ = 81871213 is a prime.

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 81872237.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81872207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40936118 + 40936119.

It is an arithmetic number, because the mean of its divisors is an integer number (40936119).

Almost surely, 2^81872237 is an apocalyptic number.

It is an amenable number.

81872237 is a deficient number, since it is larger than the sum of its proper divisors (1).

81872237 is an equidigital number, since it uses as much as digits as its factorization.

81872237 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 37632, while the sum is 38.

The square root of 81872237 is about 9048.3278565711. The cubic root of 81872237 is about 434.2223955212. Note that the first 3 decimals are identical.

The spelling of 81872237 in words is "eighty-one million, eight hundred seventy-two thousand, two hundred thirty-seven".