21223220402521 has 4 divisors (see below), whose sum is σ = 21224021275044. Its totient is φ = 21222419530000.

The previous prime is 21223220402509. The next prime is 21223220402581. The reversal of 21223220402521 is 12520402232212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16301083251600 + 4922137150921 = 4037460^2 + 2218589^2 .

It is a cyclic number.

It is not a de Polignac number, because 21223220402521 - 2⁷ = 21223220402393 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21223220402521.

It is not an unprimeable number, because it can be changed into a prime (21223220402581) 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, 400396510 + ... + 400449511.

It is an arithmetic number, because the mean of its divisors is an integer number (5306005318761).

Almost surely, 2^{21223220402521} is an apocalyptic number.

It is an amenable number.

21223220402521 is a deficient number, since it is larger than the sum of its proper divisors (800872523).

21223220402521 is an equidigital number, since it uses as much as digits as its factorization.

21223220402521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 800872522.

The product of its (nonzero) digits is 7680, while the sum is 28.

Adding to 21223220402521 its reverse (12520402232212), we get a palindrome (33743622634733).

The spelling of 21223220402521 in words is "twenty-one trillion, two hundred twenty-three billion, two hundred twenty million, four hundred two thousand, five hundred twenty-one".