81249739 has 4 divisors (see below), whose sum is σ = 81398824. Its totient is φ = 81100656.

The previous prime is 81249733. The next prime is 81249767. The reversal of 81249739 is 93794218.

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

It is a cyclic number.

It is not a de Polignac number, because 81249739 - 2⁷ = 81249611 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81249695 and 81249704.

It is not an unprimeable number, because it can be changed into a prime (81249733) 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, 73722 + ... + 74815.

It is an arithmetic number, because the mean of its divisors is an integer number (20349706).

Almost surely, 2^81249739 is an apocalyptic number.

81249739 is a deficient number, since it is larger than the sum of its proper divisors (149085).

81249739 is a wasteful number, since it uses less digits than its factorization.

81249739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149084.

The product of its digits is 108864, while the sum is 43.

The square root of 81249739 is about 9013.8637109732. The cubic root of 81249739 is about 433.1190888989.

The spelling of 81249739 in words is "eighty-one million, two hundred forty-nine thousand, seven hundred thirty-nine".