21724445635421 has 2 divisors, whose sum is σ = 21724445635422. Its totient is φ = 21724445635420.

The previous prime is 21724445635397. The next prime is 21724445635429. The reversal of 21724445635421 is 12453654442712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20177255448100 + 1547190187321 = 4491910^2 + 1243861^2 .

It is a cyclic number.

It is not a de Polignac number, because 21724445635421 - 2⁶ = 21724445635357 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21724445635421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21724445635429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10862222817710 + 10862222817711.

It is an arithmetic number, because the mean of its divisors is an integer number (10862222817711).

Almost surely, 2^{21724445635421} is an apocalyptic number.

It is an amenable number.

21724445635421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21724445635421 is an equidigital number, since it uses as much as digits as its factorization.

21724445635421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6451200, while the sum is 50.

The spelling of 21724445635421 in words is "twenty-one trillion, seven hundred twenty-four billion, four hundred forty-five million, six hundred thirty-five thousand, four hundred twenty-one".