81217897 has 4 divisors (see below), whose sum is σ = 81857536. Its totient is φ = 80578260.

The previous prime is 81217879. The next prime is 81217919. The reversal of 81217897 is 79871218.

It is a happy number.

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 81217897 - 2¹⁵ = 81185129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81218897) 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, 319629 + ... + 319882.

It is an arithmetic number, because the mean of its divisors is an integer number (20464384).

Almost surely, 2^81217897 is an apocalyptic number.

It is an amenable number.

81217897 is a deficient number, since it is larger than the sum of its proper divisors (639639).

81217897 is a wasteful number, since it uses less digits than its factorization.

81217897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 639638.

The product of its digits is 56448, while the sum is 43.

The square root of 81217897 is about 9012.0972586851. The cubic root of 81217897 is about 433.0625013118.

The spelling of 81217897 in words is "eighty-one million, two hundred seventeen thousand, eight hundred ninety-seven".