21481373 has 4 divisors (see below), whose sum is σ = 22222140. Its totient is φ = 20740608.

The previous prime is 21481337. The next prime is 21481399. The reversal of 21481373 is 37318412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13741849 + 7739524 = 3707^2 + 2782^2 .

It is a cyclic number.

It is not a de Polignac number, because 21481373 - 2⁶ = 21481309 is a prime.

It is a super-2 number, since 2×21481373² = 922898771930258, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 740737 = 21481373 / (2 + 1 + 4 + 8 + 1 + 3 + 7 + 3).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481673) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 370340 + ... + 370397.

It is an arithmetic number, because the mean of its divisors is an integer number (5555535).

Almost surely, 2^21481373 is an apocalyptic number.

It is an amenable number.

21481373 is a deficient number, since it is larger than the sum of its proper divisors (740767).

21481373 is an equidigital number, since it uses as much as digits as its factorization.

21481373 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 740766.

The product of its digits is 4032, while the sum is 29.

The square root of 21481373 is about 4634.8002114439. The cubic root of 21481373 is about 277.9845625712.

Adding to 21481373 its reverse (37318412), we get a palindrome (58799785).

The spelling of 21481373 in words is "twenty-one million, four hundred eighty-one thousand, three hundred seventy-three".