21355232405 has 16 divisors (see below), whose sum is σ = 27610967664. Its totient is φ = 15762339840.

The previous prime is 21355232399. The next prime is 21355232413. The reversal of 21355232405 is 50423255312.

It can be written as a sum of positive squares in 8 ways, for example, as 2730898564 + 18624333841 = 52258^2 + 136471^2 .

It is not a de Polignac number, because 21355232405 - 2¹⁸ = 21354970261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56327 + ... + 214203.

It is an arithmetic number, because the mean of its divisors is an integer number (1725685479).

Almost surely, 2^21355232405 is an apocalyptic number.

It is an amenable number.

21355232405 is a deficient number, since it is larger than the sum of its proper divisors (6255735259).

21355232405 is a wasteful number, since it uses less digits than its factorization.

21355232405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159976.

The product of its (nonzero) digits is 36000, while the sum is 32.

Adding to 21355232405 its reverse (50423255312), we get a palindrome (71778487717).

The spelling of 21355232405 in words is "twenty-one billion, three hundred fifty-five million, two hundred thirty-two thousand, four hundred five".