18502221721 has 4 divisors (see below), whose sum is σ = 18778374352. Its totient is φ = 18226069092.

The previous prime is 18502221713. The next prime is 18502221737. The reversal of 18502221721 is 12712220581.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18502221721 - 2³ = 18502221713 is a prime.

It is a super-2 number, since 2×18502221721² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18502221701) 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, 138076215 + ... + 138076348.

It is an arithmetic number, because the mean of its divisors is an integer number (4694593588).

Almost surely, 2^18502221721 is an apocalyptic number.

It is an amenable number.

18502221721 is a deficient number, since it is larger than the sum of its proper divisors (276152631).

18502221721 is an equidigital number, since it uses as much as digits as its factorization.

18502221721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 276152630.

The product of its (nonzero) digits is 4480, while the sum is 31.

The spelling of 18502221721 in words is "eighteen billion, five hundred two million, two hundred twenty-one thousand, seven hundred twenty-one".