81207881 has 4 divisors (see below), whose sum is σ = 85482000. Its totient is φ = 76933764.

The previous prime is 81207877. The next prime is 81207899. The reversal of 81207881 is 18870218.

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 81207881 - 2² = 81207877 is a prime.

It is a super-2 number, since 2×81207881² = 13189439873020322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81207821) 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, 2137031 + ... + 2137068.

It is an arithmetic number, because the mean of its divisors is an integer number (21370500).

Almost surely, 2^81207881 is an apocalyptic number.

It is an amenable number.

81207881 is a deficient number, since it is larger than the sum of its proper divisors (4274119).

81207881 is a wasteful number, since it uses less digits than its factorization.

81207881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4274118.

The product of its (nonzero) digits is 7168, while the sum is 35.

The square root of 81207881 is about 9011.5415440423. The cubic root of 81207881 is about 433.0446984527.

The spelling of 81207881 in words is "eighty-one million, two hundred seven thousand, eight hundred eighty-one".