21481421 has 12 divisors (see below), whose sum is σ = 24632532. Its totient is φ = 18660096.

The previous prime is 21481409. The next prime is 21481459. The reversal of 21481421 is 12418412.

It can be written as a sum of positive squares in 6 ways, for example, as 44521 + 21436900 = 211^2 + 4630^2 .

It is not a de Polignac number, because 21481421 - 2¹⁰ = 21480397 is a prime.

It is a super-2 number, since 2×21481421² = 922902896358482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481921) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 866 + ... + 6611.

It is an arithmetic number, because the mean of its divisors is an integer number (2052711).

Almost surely, 2^21481421 is an apocalyptic number.

It is an amenable number.

21481421 is a deficient number, since it is larger than the sum of its proper divisors (3151111).

21481421 is a wasteful number, since it uses less digits than its factorization.

21481421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7520 (or 7507 counting only the distinct ones).

The product of its digits is 512, while the sum is 23.

The square root of 21481421 is about 4634.8053896577. The cubic root of 21481421 is about 277.9847696226.

Adding to 21481421 its reverse (12418412), we get a palindrome (33899833).

The spelling of 21481421 in words is "twenty-one million, four hundred eighty-one thousand, four hundred twenty-one".