2156511443221 has 8 divisors (see below), whose sum is σ = 2157727128984. Its totient is φ = 2155296099840.

The previous prime is 2156511443189. The next prime is 2156511443291. The reversal of 2156511443221 is 1223441156512.

It can be written as a sum of positive squares in 4 ways, for example, as 558345200625 + 1598166242596 = 747225^2 + 1264186^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2156511443221 - 2⁵ = 2156511443189 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 (2156511443291) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13079331 + ... + 13243183.

It is an arithmetic number, because the mean of its divisors is an integer number (269715891123).

Almost surely, 2^{2156511443221} is an apocalyptic number.

It is an amenable number.

2156511443221 is a deficient number, since it is larger than the sum of its proper divisors (1215685763).

2156511443221 is a wasteful number, since it uses less digits than its factorization.

2156511443221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171191.

The product of its digits is 57600, while the sum is 37.

Adding to 2156511443221 its reverse (1223441156512), we get a palindrome (3379952599733).

The spelling of 2156511443221 in words is "two trillion, one hundred fifty-six billion, five hundred eleven million, four hundred forty-three thousand, two hundred twenty-one".