81638149 has 4 divisors (see below), whose sum is σ = 81768160. Its totient is φ = 81508140.

The previous prime is 81638147. The next prime is 81638173. The reversal of 81638149 is 94183618.

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: 94183618 = 2 ⋅47091809.

It is a cyclic number.

It is not a de Polignac number, because 81638149 - 2¹ = 81638147 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81638147) 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, 64059 + ... + 65320.

It is an arithmetic number, because the mean of its divisors is an integer number (20442040).

Almost surely, 2^81638149 is an apocalyptic number.

It is an amenable number.

81638149 is a deficient number, since it is larger than the sum of its proper divisors (130011).

81638149 is a wasteful number, since it uses less digits than its factorization.

81638149 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130010.

The product of its digits is 41472, while the sum is 40.

The square root of 81638149 is about 9035.3831684107. The cubic root of 81638149 is about 433.8081595310.

The spelling of 81638149 in words is "eighty-one million, six hundred thirty-eight thousand, one hundred forty-nine".