81638893 has 8 divisors (see below), whose sum is σ = 94580288. Its totient is φ = 69017184.

The previous prime is 81638881. The next prime is 81638911. The reversal of 81638893 is 39883618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81638893 - 2⁵ = 81638861 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 (81638803) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79371 + ... + 80392.

It is an arithmetic number, because the mean of its divisors is an integer number (11822536).

Almost surely, 2^81638893 is an apocalyptic number.

It is an amenable number.

81638893 is a deficient number, since it is larger than the sum of its proper divisors (12941395).

81638893 is a wasteful number, since it uses less digits than its factorization.

81638893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159843.

The product of its digits is 248832, while the sum is 46.

The square root of 81638893 is about 9035.4243397862. The cubic root of 81638893 is about 433.8094773475.

The spelling of 81638893 in words is "eighty-one million, six hundred thirty-eight thousand, eight hundred ninety-three".