21550987573 has 2 divisors, whose sum is σ = 21550987574. Its totient is φ = 21550987572.

The previous prime is 21550987561. The next prime is 21550987673. The reversal of 21550987573 is 37578905512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20317081444 + 1233906129 = 142538^2 + 35127^2 .

It is a cyclic number.

It is not a de Polignac number, because 21550987573 - 2⁵ = 21550987541 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21550987573.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21550987543) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775493786 + 10775493787.

It is an arithmetic number, because the mean of its divisors is an integer number (10775493787).

Almost surely, 2^21550987573 is an apocalyptic number.

It is an amenable number.

21550987573 is a deficient number, since it is larger than the sum of its proper divisors (1).

21550987573 is an equidigital number, since it uses as much as digits as its factorization.

21550987573 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2646000, while the sum is 52.

The spelling of 21550987573 in words is "twenty-one billion, five hundred fifty million, nine hundred eighty-seven thousand, five hundred seventy-three".