21252420421 has 8 divisors (see below), whose sum is σ = 21501273240. Its totient is φ = 21004634112.

The previous prime is 21252420403. The next prime is 21252420433. The reversal of 21252420421 is 12402425212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 484440100 + 20767980321 = 22010^2 + 144111^2 .

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 21252420421 - 2⁵ = 21252420389 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 (21252420401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 226506 + ... + 306283.

It is an arithmetic number, because the mean of its divisors is an integer number (2687659155).

Almost surely, 2^21252420421 is an apocalyptic number.

It is an amenable number.

21252420421 is a deficient number, since it is larger than the sum of its proper divisors (248852819).

21252420421 is a wasteful number, since it uses less digits than its factorization.

21252420421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 533255.

The product of its (nonzero) digits is 2560, while the sum is 25.

Adding to 21252420421 its reverse (12402425212), we get a palindrome (33654845633).

The spelling of 21252420421 in words is "twenty-one billion, two hundred fifty-two million, four hundred twenty thousand, four hundred twenty-one".