18915621401 has 4 divisors (see below), whose sum is σ = 19272519972. Its totient is φ = 18558722832.

The previous prime is 18915621331. The next prime is 18915621419. The reversal of 18915621401 is 10412651981.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 10412651981 = 281 ⋅37055701.

It can be written as a sum of positive squares in 2 ways, for example, as 7541185600 + 11374435801 = 86840^2 + 106651^2 .

It is a cyclic number.

It is not a de Polignac number, because 18915621401 - 2¹⁰ = 18915620377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18915621001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 178449206 + ... + 178449311.

It is an arithmetic number, because the mean of its divisors is an integer number (4818129993).

Almost surely, 2^18915621401 is an apocalyptic number.

It is an amenable number.

18915621401 is a deficient number, since it is larger than the sum of its proper divisors (356898571).

18915621401 is an equidigital number, since it uses as much as digits as its factorization.

18915621401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 356898570.

The product of its (nonzero) digits is 17280, while the sum is 38.

The spelling of 18915621401 in words is "eighteen billion, nine hundred fifteen million, six hundred twenty-one thousand, four hundred one".