81372281 has 2 divisors, whose sum is σ = 81372282. Its totient is φ = 81372280.

The previous prime is 81372223. The next prime is 81372283. The reversal of 81372281 is 18227318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81360400 + 11881 = 9020^2 + 109^2 .

It is a cyclic number.

It is not a de Polignac number, because 81372281 - 2¹⁸ = 81110137 is a prime.

It is a super-2 number, since 2×81372281² = 13242896230285922, which contains 22 as substring.

Together with 81372283, 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 (81372283) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40686140 + 40686141.

It is an arithmetic number, because the mean of its divisors is an integer number (40686141).

Almost surely, 2^81372281 is an apocalyptic number.

It is an amenable number.

81372281 is a deficient number, since it is larger than the sum of its proper divisors (1).

81372281 is an equidigital number, since it uses as much as digits as its factorization.

81372281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5376, while the sum is 32.

The square root of 81372281 is about 9020.6585679761. The cubic root of 81372281 is about 433.3367249570.

Adding to 81372281 its reverse (18227318), we get a palindrome (99599599).

The spelling of 81372281 in words is "eighty-one million, three hundred seventy-two thousand, two hundred eighty-one".