21550540409 has 2 divisors, whose sum is σ = 21550540410. Its totient is φ = 21550540408.

The previous prime is 21550540397. The next prime is 21550540441. The reversal of 21550540409 is 90404505512.

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., 14297463184 + 7253077225 = 119572^2 + 85165^2 .

It is a cyclic number.

It is not a de Polignac number, because 21550540409 - 2⁴ = 21550540393 is a prime.

It is not a weakly prime, because it can be changed into another prime (21550545409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775270204 + 10775270205.

It is an arithmetic number, because the mean of its divisors is an integer number (10775270205).

Almost surely, 2^21550540409 is an apocalyptic number.

It is an amenable number.

21550540409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21550540409 is an equidigital number, since it uses as much as digits as its factorization.

21550540409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36000, while the sum is 35.

The spelling of 21550540409 in words is "twenty-one billion, five hundred fifty million, five hundred forty thousand, four hundred nine".