21481311 has 4 divisors (see below), whose sum is σ = 28641752. Its totient is φ = 14320872.

The previous prime is 21481309. The next prime is 21481331. The reversal of 21481311 is 11318412.

It is a happy number.

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

It is not a de Polignac number, because 21481311 - 2¹ = 21481309 is a prime.

It is a super-2 number, since 2×21481311² = 922893444557442, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481301) 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, 3580216 + ... + 3580221.

It is an arithmetic number, because the mean of its divisors is an integer number (7160438).

Almost surely, 2^21481311 is an apocalyptic number.

21481311 is a deficient number, since it is larger than the sum of its proper divisors (7160441).

21481311 is an equidigital number, since it uses as much as digits as its factorization.

21481311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7160440.

The product of its digits is 192, while the sum is 21.

The square root of 21481311 is about 4634.7935229091. The cubic root of 21481311 is about 277.9842951292.

Adding to 21481311 its reverse (11318412), we get a palindrome (32799723).

The spelling of 21481311 in words is "twenty-one million, four hundred eighty-one thousand, three hundred eleven".