16215181221 has 4 divisors (see below), whose sum is σ = 21620241632. Its totient is φ = 10810120812.

The previous prime is 16215181211. The next prime is 16215181231. The reversal of 16215181221 is 12218151261.

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 an interprime number because it is at equal distance from previous prime (16215181211) and next prime (16215181231).

It is not a de Polignac number, because 16215181221 - 2⁵ = 16215181189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16215181211) 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, 2702530201 + ... + 2702530206.

It is an arithmetic number, because the mean of its divisors is an integer number (5405060408).

Almost surely, 2^16215181221 is an apocalyptic number.

It is an amenable number.

16215181221 is a deficient number, since it is larger than the sum of its proper divisors (5405060411).

16215181221 is an equidigital number, since it uses as much as digits as its factorization.

16215181221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5405060410.

The product of its digits is 1920, while the sum is 30.

The spelling of 16215181221 in words is "sixteen billion, two hundred fifteen million, one hundred eighty-one thousand, two hundred twenty-one".