1815990031221 has 16 divisors (see below), whose sum is σ = 2564046586368. Its totient is φ = 1139313190400.

The previous prime is 1815990031183. The next prime is 1815990031279. The reversal of 1815990031221 is 1221300995181.

It is a cyclic number.

It is not a de Polignac number, because 1815990031221 - 2²³ = 1815981642613 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1815990030221) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1608165 + ... + 2493626.

It is an arithmetic number, because the mean of its divisors is an integer number (160252911648).

Almost surely, 2^{1815990031221} is an apocalyptic number.

It is an amenable number.

1815990031221 is a deficient number, since it is larger than the sum of its proper divisors (748056555147).

1815990031221 is a wasteful number, since it uses less digits than its factorization.

1815990031221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4110492.

The product of its (nonzero) digits is 38880, while the sum is 42.

The spelling of 1815990031221 in words is "one trillion, eight hundred fifteen billion, nine hundred ninety million, thirty-one thousand, two hundred twenty-one".