21213555542521 has 2 divisors, whose sum is σ = 21213555542522. Its totient is φ = 21213555542520.

The previous prime is 21213555542513. The next prime is 21213555542539. The reversal of 21213555542521 is 12524555531212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15808488528121 + 5405067014400 = 3975989^2 + 2324880^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213555542521 - 2³ = 21213555542513 is a prime.

It is not a weakly prime, because it can be changed into another prime (21213555542551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606777771260 + 10606777771261.

It is an arithmetic number, because the mean of its divisors is an integer number (10606777771261).

Almost surely, 2^{21213555542521} is an apocalyptic number.

It is an amenable number.

21213555542521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213555542521 is an equidigital number, since it uses as much as digits as its factorization.

21213555542521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 600000, while the sum is 43.

The spelling of 21213555542521 in words is "twenty-one trillion, two hundred thirteen billion, five hundred fifty-five million, five hundred forty-two thousand, five hundred twenty-one".