21232121605 has 4 divisors (see below), whose sum is σ = 25478545932. Its totient is φ = 16985697280.

The previous prime is 21232121597. The next prime is 21232121623. The reversal of 21232121605 is 50612123212.

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 9385540641 + 11846580964 = 96879^2 + 108842^2 .

It is not a de Polignac number, because 21232121605 - 2³ = 21232121597 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21232121605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2123212156 + ... + 2123212165.

It is an arithmetic number, because the mean of its divisors is an integer number (6369636483).

Almost surely, 2^21232121605 is an apocalyptic number.

It is an amenable number.

21232121605 is a deficient number, since it is larger than the sum of its proper divisors (4246424327).

21232121605 is an equidigital number, since it uses as much as digits as its factorization.

21232121605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4246424326.

The product of its (nonzero) digits is 1440, while the sum is 25.

Adding to 21232121605 its reverse (50612123212), we get a palindrome (71844244817).

The spelling of 21232121605 in words is "twenty-one billion, two hundred thirty-two million, one hundred twenty-one thousand, six hundred five".