81949251 has 4 divisors (see below), whose sum is σ = 109265672. Its totient is φ = 54632832.

The previous prime is 81949237. The next prime is 81949297. The reversal of 81949251 is 15294918.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81949251 - 2¹⁴ = 81932867 is a prime.

It is a super-2 number, since 2×81949251² = 13431359478922002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81949211) 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, 13658206 + ... + 13658211.

It is an arithmetic number, because the mean of its divisors is an integer number (27316418).

Almost surely, 2^81949251 is an apocalyptic number.

81949251 is a deficient number, since it is larger than the sum of its proper divisors (27316421).

81949251 is a wasteful number, since it uses less digits than its factorization.

81949251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27316420.

The product of its digits is 25920, while the sum is 39.

The square root of 81949251 is about 9052.5825596898. The cubic root of 81949251 is about 434.3585048409.

The spelling of 81949251 in words is "eighty-one million, nine hundred forty-nine thousand, two hundred fifty-one".