21213542790809 has 2 divisors, whose sum is σ = 21213542790810. Its totient is φ = 21213542790808.

The previous prime is 21213542790799. The next prime is 21213542790871. The reversal of 21213542790809 is 90809724531212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11502591053209 + 9710951737600 = 3391547^2 + 3116240^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213542790809 - 2²⁸ = 21213274355353 is a prime.

It is not a weakly prime, because it can be changed into another prime (21213542790409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606771395404 + 10606771395405.

It is an arithmetic number, because the mean of its divisors is an integer number (10606771395405).

Almost surely, 2^{21213542790809} is an apocalyptic number.

It is an amenable number.

21213542790809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213542790809 is an equidigital number, since it uses as much as digits as its factorization.

21213542790809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2177280, while the sum is 53.

The spelling of 21213542790809 in words is "twenty-one trillion, two hundred thirteen billion, five hundred forty-two million, seven hundred ninety thousand, eight hundred nine".