21043400405 has 8 divisors (see below), whose sum is σ = 25316998200. Its totient is φ = 16791441856.

The previous prime is 21043400393. The next prime is 21043400449. The reversal of 21043400405 is 50400434012.

It can be written as a sum of positive squares in 4 ways, for example, as 97495876 + 20945904529 = 9874^2 + 144727^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21043400405 - 2²⁸ = 20774964949 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5407670 + ... + 5411559.

It is an arithmetic number, because the mean of its divisors is an integer number (3164624775).

Almost surely, 2^21043400405 is an apocalyptic number.

It is an amenable number.

21043400405 is a deficient number, since it is larger than the sum of its proper divisors (4273597795).

21043400405 is a wasteful number, since it uses less digits than its factorization.

21043400405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10819623.

The product of its (nonzero) digits is 1920, while the sum is 23.

Adding to 21043400405 its reverse (50400434012), we get a palindrome (71443834417).

The spelling of 21043400405 in words is "twenty-one billion, forty-three million, four hundred thousand, four hundred five".