81020993 has 4 divisors (see below), whose sum is σ = 82349268. Its totient is φ = 79692720.

The previous prime is 81020981. The next prime is 81020999. The reversal of 81020993 is 39902018.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16507969 + 64513024 = 4063^2 + 8032^2 .

It is a cyclic number.

It is not a de Polignac number, because 81020993 - 2⁴ = 81020977 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81020999) 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, 664046 + ... + 664167.

It is an arithmetic number, because the mean of its divisors is an integer number (20587317).

Almost surely, 2^81020993 is an apocalyptic number.

It is an amenable number.

81020993 is a deficient number, since it is larger than the sum of its proper divisors (1328275).

81020993 is a wasteful number, since it uses less digits than its factorization.

81020993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1328274.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 81020993 is about 9001.1662022207. The cubic root of 81020993 is about 432.7122470551.

The spelling of 81020993 in words is "eighty-one million, twenty thousand, nine hundred ninety-three".