21154521552221 has 2 divisors, whose sum is σ = 21154521552222. Its totient is φ = 21154521552220.

The previous prime is 21154521552181. The next prime is 21154521552247. The reversal of 21154521552221 is 12225512545112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19615916988196 + 1538604564025 = 4428986^2 + 1240405^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154521552221 - 2²² = 21154517357917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21154521552251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577260776110 + 10577260776111.

It is an arithmetic number, because the mean of its divisors is an integer number (10577260776111).

Almost surely, 2^{21154521552221} is an apocalyptic number.

It is an amenable number.

21154521552221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154521552221 is an equidigital number, since it uses as much as digits as its factorization.

21154521552221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80000, while the sum is 38.

The spelling of 21154521552221 in words is "twenty-one trillion, one hundred fifty-four billion, five hundred twenty-one million, five hundred fifty-two thousand, two hundred twenty-one".