81861893 has 4 divisors (see below), whose sum is σ = 82188288. Its totient is φ = 81535500.

The previous prime is 81861887. The next prime is 81861907. The reversal of 81861893 is 39816818.

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 81861893 - 2⁴ = 81861877 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 (81861803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 162821 + ... + 163322.

It is an arithmetic number, because the mean of its divisors is an integer number (20547072).

Almost surely, 2^81861893 is an apocalyptic number.

It is an amenable number.

81861893 is a deficient number, since it is larger than the sum of its proper divisors (326395).

81861893 is a wasteful number, since it uses less digits than its factorization.

81861893 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 326394.

The product of its digits is 82944, while the sum is 44.

The square root of 81861893 is about 9047.7562411904. The cubic root of 81861893 is about 434.2041077361.

The spelling of 81861893 in words is "eighty-one million, eight hundred sixty-one thousand, eight hundred ninety-three".