21248381 has 16 divisors (see below), whose sum is σ = 26749440. Its totient is φ = 16396080.

The previous prime is 21248369. The next prime is 21248401. The reversal of 21248381 is 18384212.

It is a cyclic number.

It is not a de Polignac number, because 21248381 - 2¹⁸ = 20986237 is a prime.

It is a super-2 number, since 2×21248381² = 902987390242322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21248081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6950 + ... + 9528.

It is an arithmetic number, because the mean of its divisors is an integer number (1671840).

Almost surely, 2^21248381 is an apocalyptic number.

It is an amenable number.

21248381 is a deficient number, since it is larger than the sum of its proper divisors (5501059).

21248381 is a wasteful number, since it uses less digits than its factorization.

21248381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2704.

The product of its digits is 3072, while the sum is 29.

The square root of 21248381 is about 4609.5966200959. The cubic root of 21248381 is about 276.9758783793.

The spelling of 21248381 in words is "twenty-one million, two hundred forty-eight thousand, three hundred eighty-one".