21240401 has 16 divisors (see below), whose sum is σ = 26412288. Its totient is φ = 16632000.

The previous prime is 21240391. The next prime is 21240403. The reversal of 21240401 is 10404212.

It is not a de Polignac number, because 21240401 - 2¹⁸ = 20978257 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21240403) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8036 + ... + 10346.

It is an arithmetic number, because the mean of its divisors is an integer number (1650768).

Almost surely, 2^21240401 is an apocalyptic number.

It is an amenable number.

21240401 is a deficient number, since it is larger than the sum of its proper divisors (5171887).

21240401 is a wasteful number, since it uses less digits than its factorization.

21240401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2432.

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21240401 is about 4608.7309533102. The cubic root of 21240401 is about 276.9412005331.

Adding to 21240401 its reverse (10404212), we get a palindrome (31644613).

The spelling of 21240401 in words is "twenty-one million, two hundred forty thousand, four hundred one".