81689893 has 4 divisors (see below), whose sum is σ = 81754848. Its totient is φ = 81624940.

The previous prime is 81689869. The next prime is 81689921. The reversal of 81689893 is 39898618.

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 81689893 - 2²¹ = 79592741 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81689893.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689843) 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, 30553 + ... + 33118.

It is an arithmetic number, because the mean of its divisors is an integer number (20438712).

Almost surely, 2^81689893 is an apocalyptic number.

It is an amenable number.

81689893 is a deficient number, since it is larger than the sum of its proper divisors (64955).

81689893 is a wasteful number, since it uses less digits than its factorization.

81689893 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64954.

The product of its digits is 746496, while the sum is 52.

The square root of 81689893 is about 9038.2461241106. The cubic root of 81689893 is about 433.8997924620.

It can be divided in two parts, 816 and 89893, that added together give a palindrome (90709).

The spelling of 81689893 in words is "eighty-one million, six hundred eighty-nine thousand, eight hundred ninety-three".