81449993 has 4 divisors (see below), whose sum is σ = 82597248. Its totient is φ = 80302740.

The previous prime is 81449983. The next prime is 81450001. The reversal of 81449993 is 39994418.

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: 39994418 = 2 ⋅19997209.

It is a cyclic number.

It is not a de Polignac number, because 81449993 - 2²⁰ = 80401417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81449983) 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, 573521 + ... + 573662.

It is an arithmetic number, because the mean of its divisors is an integer number (20649312).

Almost surely, 2^81449993 is an apocalyptic number.

It is an amenable number.

81449993 is a deficient number, since it is larger than the sum of its proper divisors (1147255).

81449993 is a wasteful number, since it uses less digits than its factorization.

81449993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1147254.

The product of its digits is 279936, while the sum is 47.

The square root of 81449993 is about 9024.9649860817. The cubic root of 81449993 is about 433.4746292024.

The spelling of 81449993 in words is "eighty-one million, four hundred forty-nine thousand, nine hundred ninety-three".