21326011621 has 2 divisors, whose sum is σ = 21326011622. Its totient is φ = 21326011620.

The previous prime is 21326011613. The next prime is 21326011639. The reversal of 21326011621 is 12611062312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16824943521 + 4501068100 = 129711^2 + 67090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21326011621 - 2³ = 21326011613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21326011661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10663005810 + 10663005811.

It is an arithmetic number, because the mean of its divisors is an integer number (10663005811).

Almost surely, 2^21326011621 is an apocalyptic number.

It is an amenable number.

21326011621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21326011621 is an equidigital number, since it uses as much as digits as its factorization.

21326011621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 25.

Adding to 21326011621 its reverse (12611062312), we get a palindrome (33937073933).

The spelling of 21326011621 in words is "twenty-one billion, three hundred twenty-six million, eleven thousand, six hundred twenty-one".