21481387 has 8 divisors (see below), whose sum is σ = 22972032. Its totient is φ = 20016000.

The previous prime is 21481337. The next prime is 21481399. The reversal of 21481387 is 78318412.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21481387 - 2⁷ = 21481259 is a prime.

It is a super-2 number, since 2×21481387² = 922899974887538, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21481337) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4539 + ... + 7972.

It is an arithmetic number, because the mean of its divisors is an integer number (2871504).

Almost surely, 2^21481387 is an apocalyptic number.

21481387 is a deficient number, since it is larger than the sum of its proper divisors (1490645).

21481387 is a wasteful number, since it uses less digits than its factorization.

21481387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12629.

The product of its digits is 10752, while the sum is 34.

The square root of 21481387 is about 4634.8017217568. The cubic root of 21481387 is about 277.9846229612.

Adding to 21481387 its reverse (78318412), we get a palindrome (99799799).

The spelling of 21481387 in words is "twenty-one million, four hundred eighty-one thousand, three hundred eighty-seven".