81906081 has 4 divisors (see below), whose sum is σ = 109208112. Its totient is φ = 54604052.

The previous prime is 81906067. The next prime is 81906107. The reversal of 81906081 is 18060918.

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 81906081 - 2¹⁵ = 81873313 is a prime.

It is a super-2 number, since 2×81906081² = 13417212209557122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81906031) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13651011 + ... + 13651016.

It is an arithmetic number, because the mean of its divisors is an integer number (27302028).

Almost surely, 2^81906081 is an apocalyptic number.

It is an amenable number.

81906081 is a deficient number, since it is larger than the sum of its proper divisors (27302031).

81906081 is a wasteful number, since it uses less digits than its factorization.

81906081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27302030.

The product of its (nonzero) digits is 3456, while the sum is 33.

The square root of 81906081 is about 9050.1978431413. The cubic root of 81906081 is about 434.2822196195.

Adding to 81906081 its reverse (18060918), we get a palindrome (99966999).

The spelling of 81906081 in words is "eighty-one million, nine hundred six thousand, eighty-one".