21373281 has 16 divisors (see below), whose sum is σ = 32203200. Its totient is φ = 14006304.

The previous prime is 21373277. The next prime is 21373327. The reversal of 21373281 is 18237312.

It is not a de Polignac number, because 21373281 - 2² = 21373277 is a prime.

It is a super-2 number, since 2×21373281² = 913634281409922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21371281) 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, 5116 + ... + 8301.

It is an arithmetic number, because the mean of its divisors is an integer number (2012700).

Almost surely, 2^21373281 is an apocalyptic number.

It is an amenable number.

21373281 is a deficient number, since it is larger than the sum of its proper divisors (10829919).

21373281 is a wasteful number, since it uses less digits than its factorization.

21373281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13485 (or 13479 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21373281 is about 4623.1245927403. The cubic root of 21373281 is about 277.5175153298.

The spelling of 21373281 in words is "twenty-one million, three hundred seventy-three thousand, two hundred eighty-one".