81638210 has 8 divisors (see below), whose sum is σ = 146948796. Its totient is φ = 32655280.

The previous prime is 81638203. The next prime is 81638213. The reversal of 81638210 is 1283618.

It can be written as a sum of positive squares in 2 ways, for example, as 71250481 + 10387729 = 8441^2 + 3223^2 .

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

It is not an unprimeable number, because it can be changed into a prime (81638213) 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, 4081901 + ... + 4081920.

Almost surely, 2^81638210 is an apocalyptic number.

81638210 is a deficient number, since it is larger than the sum of its proper divisors (65310586).

81638210 is a wasteful number, since it uses less digits than its factorization.

81638210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8163828.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 81638210 is about 9035.3865440279. The cubic root of 81638210 is about 433.8082675781.

The spelling of 81638210 in words is "eighty-one million, six hundred thirty-eight thousand, two hundred ten".