21072481 has 2 divisors, whose sum is σ = 21072482. Its totient is φ = 21072480.

The previous prime is 21072449. The next prime is 21072487. The reversal of 21072481 is 18427012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10890000 + 10182481 = 3300^2 + 3191^2 .

It is a cyclic number.

It is not a de Polignac number, because 21072481 - 2⁵ = 21072449 is a prime.

It is a super-2 number, since 2×21072481² = 888098910990722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21072487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10536240 + 10536241.

It is an arithmetic number, because the mean of its divisors is an integer number (10536241).

Almost surely, 2^21072481 is an apocalyptic number.

It is an amenable number.

21072481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21072481 is an equidigital number, since it uses as much as digits as its factorization.

21072481 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21072481 is about 4590.4772083085. The cubic root of 21072481 is about 276.2094651936.

Adding to 21072481 its reverse (18427012), we get a palindrome (39499493).

The spelling of 21072481 in words is "twenty-one million, seventy-two thousand, four hundred eighty-one".