21524587409 has 4 divisors (see below), whose sum is σ = 23180324916. Its totient is φ = 19868849904.

The previous prime is 21524587397. The next prime is 21524587453. The reversal of 21524587409 is 90478542512.

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 859662400 + 20664925009 = 29320^2 + 143753^2 .

It is a cyclic number.

It is not a de Polignac number, because 21524587409 - 2⁴ = 21524587393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21524587109) 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, 827868734 + ... + 827868759.

It is an arithmetic number, because the mean of its divisors is an integer number (5795081229).

Almost surely, 2^21524587409 is an apocalyptic number.

It is an amenable number.

21524587409 is a deficient number, since it is larger than the sum of its proper divisors (1655737507).

21524587409 is a wasteful number, since it uses less digits than its factorization.

21524587409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1655737506.

The product of its (nonzero) digits is 806400, while the sum is 47.

The spelling of 21524587409 in words is "twenty-one billion, five hundred twenty-four million, five hundred eighty-seven thousand, four hundred nine".