21938840409 has 16 divisors (see below), whose sum is σ = 30987490880. Its totient is φ = 13767848640.

The previous prime is 21938840389. The next prime is 21938840437. The reversal of 21938840409 is 90404883912.

It is not a de Polignac number, because 21938840409 - 2²⁹ = 21401969497 is a prime.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21938840479) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1216822 + ... + 1234719.

It is an arithmetic number, because the mean of its divisors is an integer number (1936718180).

Almost surely, 2^21938840409 is an apocalyptic number.

It is an amenable number.

21938840409 is a deficient number, since it is larger than the sum of its proper divisors (9048650471).

21938840409 is a wasteful number, since it uses less digits than its factorization.

21938840409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2451720.

The product of its (nonzero) digits is 497664, while the sum is 48.

The spelling of 21938840409 in words is "twenty-one billion, nine hundred thirty-eight million, eight hundred forty thousand, four hundred nine".