81989563 has 4 divisors (see below), whose sum is σ = 82038088. Its totient is φ = 81941040.

The previous prime is 81989539. The next prime is 81989591. The reversal of 81989563 is 36598918.

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 81989563 - 2²¹ = 79892411 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81989533) 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, 21633 + ... + 25138.

It is an arithmetic number, because the mean of its divisors is an integer number (20509522).

Almost surely, 2^81989563 is an apocalyptic number.

81989563 is a deficient number, since it is larger than the sum of its proper divisors (48525).

81989563 is a wasteful number, since it uses less digits than its factorization.

81989563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48524.

The product of its digits is 466560, while the sum is 49.

The square root of 81989563 is about 9054.8088328799. The cubic root of 81989563 is about 434.4297155374.

The spelling of 81989563 in words is "eighty-one million, nine hundred eighty-nine thousand, five hundred sixty-three".