81581037 has 4 divisors (see below), whose sum is σ = 108774720. Its totient is φ = 54387356.

The previous prime is 81581029. The next prime is 81581051. The reversal of 81581037 is 73018518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81581037 - 2³ = 81581029 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81580989 and 81581007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81581737) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13596837 + ... + 13596842.

It is an arithmetic number, because the mean of its divisors is an integer number (27193680).

Almost surely, 2^81581037 is an apocalyptic number.

It is an amenable number.

81581037 is a deficient number, since it is larger than the sum of its proper divisors (27193683).

81581037 is a wasteful number, since it uses less digits than its factorization.

81581037 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27193682.

The product of its (nonzero) digits is 6720, while the sum is 33.

The square root of 81581037 is about 9032.2221518295. Note that the first 3 decimals coincide. The cubic root of 81581037 is about 433.7069754986.

The spelling of 81581037 in words is "eighty-one million, five hundred eighty-one thousand, thirty-seven".