21405042125413 has 4 divisors (see below), whose sum is σ = 21417867197260. Its totient is φ = 21392217053568.

The previous prime is 21405042125399. The next prime is 21405042125437. The reversal of 21405042125413 is 31452124050412.

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 11566644554529 + 9838397570884 = 3400977^2 + 3136622^2 .

It is a cyclic number.

It is not a de Polignac number, because 21405042125413 - 2⁹ = 21405042124901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405042125473) 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, 6412533420 + ... + 6412536757.

It is an arithmetic number, because the mean of its divisors is an integer number (5354466799315).

Almost surely, 2^{21405042125413} is an apocalyptic number.

It is an amenable number.

21405042125413 is a deficient number, since it is larger than the sum of its proper divisors (12825071847).

21405042125413 is a wasteful number, since it uses less digits than its factorization.

21405042125413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12825071846.

The product of its (nonzero) digits is 38400, while the sum is 34.

Adding to 21405042125413 its reverse (31452124050412), we get a palindrome (52857166175825).

The spelling of 21405042125413 in words is "twenty-one trillion, four hundred five billion, forty-two million, one hundred twenty-five thousand, four hundred thirteen".