81887213 has 16 divisors (see below), whose sum is σ = 88627200. Its totient is φ = 75479040.

The previous prime is 81887203. The next prime is 81887237. The reversal of 81887213 is 31278818.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81887213 is a prime.

It is a super-3 number, since 3×81887213³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81887203) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 70445 + ... + 71597.

It is an arithmetic number, because the mean of its divisors is an integer number (5539200).

Almost surely, 2^81887213 is an apocalyptic number.

It is an amenable number.

81887213 is a deficient number, since it is larger than the sum of its proper divisors (6739987).

81887213 is a wasteful number, since it uses less digits than its factorization.

81887213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1292.

The product of its digits is 21504, while the sum is 38.

The square root of 81887213 is about 9049.1553749507. The cubic root of 81887213 is about 434.2488697709.

The spelling of 81887213 in words is "eighty-one million, eight hundred eighty-seven thousand, two hundred thirteen".