81506837 has 2 divisors, whose sum is σ = 81506838. Its totient is φ = 81506836.

The previous prime is 81506771. The next prime is 81506839. The reversal of 81506837 is 73860518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80748196 + 758641 = 8986^2 + 871^2 .

It is a cyclic number.

It is not a de Polignac number, because 81506837 - 2¹² = 81502741 is a prime.

Together with 81506839, 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 81506837.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81506839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40753418 + 40753419.

It is an arithmetic number, because the mean of its divisors is an integer number (40753419).

Almost surely, 2^81506837 is an apocalyptic number.

It is an amenable number.

81506837 is a deficient number, since it is larger than the sum of its proper divisors (1).

81506837 is an equidigital number, since it uses as much as digits as its factorization.

81506837 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40320, while the sum is 38.

The square root of 81506837 is about 9028.1137011006. The cubic root of 81506837 is about 433.5754464890.

The spelling of 81506837 in words is "eighty-one million, five hundred six thousand, eight hundred thirty-seven".