21420243401 has 4 divisors (see below), whose sum is σ = 21942688404. Its totient is φ = 20897798400.

The previous prime is 21420243379. The next prime is 21420243433. The reversal of 21420243401 is 10434202412.

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 10237392400 + 11182851001 = 101180^2 + 105749^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21420243401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21420246401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 261222440 + ... + 261222521.

It is an arithmetic number, because the mean of its divisors is an integer number (5485672101).

Almost surely, 2^21420243401 is an apocalyptic number.

It is an amenable number.

21420243401 is a deficient number, since it is larger than the sum of its proper divisors (522445003).

21420243401 is an equidigital number, since it uses as much as digits as its factorization.

21420243401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 522445002.

The product of its (nonzero) digits is 1536, while the sum is 23.

Adding to 21420243401 its reverse (10434202412), we get a palindrome (31854445813).

The spelling of 21420243401 in words is "twenty-one billion, four hundred twenty million, two hundred forty-three thousand, four hundred one".