81397 has 4 divisors (see below), whose sum is σ = 84960. Its totient is φ = 77836.

The previous prime is 81373. The next prime is 81401. The reversal of 81397 is 79318.

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, and also an emirpimes, since its reverse is a distinct semiprime: 79318 = 2 ⋅39659.

It is a cyclic number.

It is not a de Polignac number, because 81397 - 2¹¹ = 79349 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81307) 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, 1747 + ... + 1792.

It is an arithmetic number, because the mean of its divisors is an integer number (21240).

2⁸¹³⁹⁷ is an apocalyptic number.

81397 is the 153-rd centered heptagonal number.

It is an amenable number.

81397 is a deficient number, since it is larger than the sum of its proper divisors (3563).

81397 is a wasteful number, since it uses less digits than its factorization.

81397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3562.

The product of its digits is 1512, while the sum is 28.

The square root of 81397 is about 285.3015948080. The cubic root of 81397 is about 43.3380599709.

The spelling of 81397 in words is "eighty-one thousand, three hundred ninety-seven".