81438769 has 4 divisors (see below), whose sum is σ = 85725040. Its totient is φ = 77152500.

The previous prime is 81438683. The next prime is 81438787. The reversal of 81438769 is 96783418.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 81438769 - 2²⁵ = 47884337 is a prime.

It is a super-2 number, since 2×81438769² = 13264546192470722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81435769) 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, 2143107 + ... + 2143144.

It is an arithmetic number, because the mean of its divisors is an integer number (21431260).

Almost surely, 2^81438769 is an apocalyptic number.

It is an amenable number.

81438769 is a deficient number, since it is larger than the sum of its proper divisors (4286271).

81438769 is a wasteful number, since it uses less digits than its factorization.

81438769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4286270.

The product of its digits is 290304, while the sum is 46.

The square root of 81438769 is about 9024.3431339904. The cubic root of 81438769 is about 433.4547170144.

The spelling of 81438769 in words is "eighty-one million, four hundred thirty-eight thousand, seven hundred sixty-nine".