15321809981 has 4 divisors (see below), whose sum is σ = 15325347132. Its totient is φ = 15318272832.

The previous prime is 15321809959. The next prime is 15321809983. The reversal of 15321809981 is 18990812351.

It is a happy number.

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 7855985956 + 7465824025 = 88634^2 + 86405^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15321809981 is a prime.

It is a super-2 number, since 2×15321809981² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15321809983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1762070 + ... + 1770743.

It is an arithmetic number, because the mean of its divisors is an integer number (3831336783).

Almost surely, 2^15321809981 is an apocalyptic number.

It is an amenable number.

15321809981 is a deficient number, since it is larger than the sum of its proper divisors (3537151).

15321809981 is an equidigital number, since it uses as much as digits as its factorization.

15321809981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3537150.

The product of its (nonzero) digits is 155520, while the sum is 47.

The spelling of 15321809981 in words is "fifteen billion, three hundred twenty-one million, eight hundred nine thousand, nine hundred eighty-one".