21042042401 has 4 divisors (see below), whose sum is σ = 21767630100. Its totient is φ = 20316454704.

The previous prime is 21042042397. The next prime is 21042042409. The reversal of 21042042401 is 10424024012.

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 9360756001 + 11681286400 = 96751^2 + 108080^2 .

It is a cyclic number.

It is not a de Polignac number, because 21042042401 - 2² = 21042042397 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21042042409) 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, 362793806 + ... + 362793863.

It is an arithmetic number, because the mean of its divisors is an integer number (5441907525).

Almost surely, 2^21042042401 is an apocalyptic number.

It is an amenable number.

21042042401 is a deficient number, since it is larger than the sum of its proper divisors (725587699).

21042042401 is an equidigital number, since it uses as much as digits as its factorization.

21042042401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 725587698.

The product of its (nonzero) digits is 512, while the sum is 20.

Adding to 21042042401 its reverse (10424024012), we get a palindrome (31466066413).

The spelling of 21042042401 in words is "twenty-one billion, forty-two million, forty-two thousand, four hundred one".