81906149 has 4 divisors (see below), whose sum is σ = 88206636. Its totient is φ = 75605664.

The previous prime is 81906113. The next prime is 81906193. The reversal of 81906149 is 94160918.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 94160918 = 2 ⋅47080459.

It can be written as a sum of positive squares in 2 ways, for example, as 21921124 + 59985025 = 4682^2 + 7745^2 .

It is a cyclic number.

It is not a de Polignac number, because 81906149 - 2¹⁶ = 81840613 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 (81906109) 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, 3150224 + ... + 3150249.

It is an arithmetic number, because the mean of its divisors is an integer number (22051659).

Almost surely, 2^81906149 is an apocalyptic number.

It is an amenable number.

81906149 is a deficient number, since it is larger than the sum of its proper divisors (6300487).

81906149 is a wasteful number, since it uses less digits than its factorization.

81906149 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6300486.

The product of its (nonzero) digits is 15552, while the sum is 38.

The square root of 81906149 is about 9050.2015999645. The cubic root of 81906149 is about 434.2823398026.

The spelling of 81906149 in words is "eighty-one million, nine hundred six thousand, one hundred forty-nine".