21908881945 has 4 divisors (see below), whose sum is σ = 26290658340. Its totient is φ = 17527105552.

The previous prime is 21908881877. The next prime is 21908881949. The reversal of 21908881945 is 54918880912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7615005696 + 14293876249 = 87264^2 + 119557^2 .

It is a cyclic number.

It is not a de Polignac number, because 21908881945 - 2¹⁷ = 21908750873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21908881949) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2190888190 + ... + 2190888199.

It is an arithmetic number, because the mean of its divisors is an integer number (6572664585).

Almost surely, 2^21908881945 is an apocalyptic number.

It is an amenable number.

21908881945 is a deficient number, since it is larger than the sum of its proper divisors (4381776395).

21908881945 is an equidigital number, since it uses as much as digits as its factorization.

21908881945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4381776394.

The product of its (nonzero) digits is 1658880, while the sum is 55.

The spelling of 21908881945 in words is "twenty-one billion, nine hundred eight million, eight hundred eighty-one thousand, nine hundred forty-five".