21784874409 has 9 divisors (see below), whose sum is σ = 31467680413. Its totient is φ = 14522954412.

The previous prime is 21784874389. The next prime is 21784874431. The reversal of 21784874409 is 90447848712.

The square root of 21784874409 is 147597.

It is a perfect power (a square), and thus also a powerful number.

It is a tau number, because it is divible by the number of its divisors (9).

It is a de Polignac number, because none of the positive numbers 2^k-21784874409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21784874509) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 418192 + ... + 467390.

Almost surely, 2^21784874409 is an apocalyptic number.

21784874409 is the 147597-th square number.

21784874409 is the 73799-th centered octagonal number.

It is an amenable number.

21784874409 is a deficient number, since it is larger than the sum of its proper divisors (9682806004).

21784874409 is an frugal number, since it uses more digits than its factorization.

21784874409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98404 (or 49202 counting only the distinct ones).

The product of its (nonzero) digits is 3612672, while the sum is 54.

The spelling of 21784874409 in words is "twenty-one billion, seven hundred eighty-four million, eight hundred seventy-four thousand, four hundred nine".