81072149 has 4 divisors (see below), whose sum is σ = 81093036. Its totient is φ = 81051264.

The previous prime is 81072137. The next prime is 81072163. The reversal of 81072149 is 94127018.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 94127018 = 2 ⋅47063509.

It can be written as a sum of positive squares in 2 ways, for example, as 27636049 + 53436100 = 5257^2 + 7310^2 .

It is a cyclic number.

It is not a de Polignac number, because 81072149 - 2¹⁶ = 81006613 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 (81072109) 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, 2714 + ... + 13019.

It is an arithmetic number, because the mean of its divisors is an integer number (20273259).

Almost surely, 2^81072149 is an apocalyptic number.

It is an amenable number.

81072149 is a deficient number, since it is larger than the sum of its proper divisors (20887).

81072149 is a wasteful number, since it uses less digits than its factorization.

81072149 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20886.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 81072149 is about 9004.0073856034. The cubic root of 81072149 is about 432.8032982330.

The spelling of 81072149 in words is "eighty-one million, seventy-two thousand, one hundred forty-nine".