21221431405 has 4 divisors (see below), whose sum is σ = 25465717692. Its totient is φ = 16977145120.

The previous prime is 21221431369. The next prime is 21221431433. The reversal of 21221431405 is 50413412212.

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 11047481449 + 10173949956 = 105107^2 + 100866^2 .

It is not a de Polignac number, because 21221431405 - 2⁷ = 21221431277 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 21221431405.

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, 2122143136 + ... + 2122143145.

It is an arithmetic number, because the mean of its divisors is an integer number (6366429423).

Almost surely, 2^21221431405 is an apocalyptic number.

It is an amenable number.

21221431405 is a deficient number, since it is larger than the sum of its proper divisors (4244286287).

21221431405 is an equidigital number, since it uses as much as digits as its factorization.

21221431405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4244286286.

The product of its (nonzero) digits is 1920, while the sum is 25.

Adding to 21221431405 its reverse (50413412212), we get a palindrome (71634843617).

The spelling of 21221431405 in words is "twenty-one billion, two hundred twenty-one million, four hundred thirty-one thousand, four hundred five".