21424401 has 6 divisors (see below), whose sum is σ = 30946370. Its totient is φ = 14282928.

The previous prime is 21424397. The next prime is 21424409. The reversal of 21424401 is 10442412.

It can be written as a sum of positive squares in only one way, i.e., 20657025 + 767376 = 4545^2 + 876^2 .

It is not a de Polignac number, because 21424401 - 2² = 21424397 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21424409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1190236 + ... + 1190253.

Almost surely, 2^21424401 is an apocalyptic number.

It is an amenable number.

21424401 is a deficient number, since it is larger than the sum of its proper divisors (9521969).

21424401 is a wasteful number, since it uses less digits than its factorization.

21424401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2380495 (or 2380492 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 21424401 is about 4628.6500191741. The cubic root of 21424401 is about 277.7385919775.

Adding to 21424401 its reverse (10442412), we get a palindrome (31866813).

The spelling of 21424401 in words is "twenty-one million, four hundred twenty-four thousand, four hundred one".