21387229 has 4 divisors (see below), whose sum is σ = 21594976. Its totient is φ = 21179484.

The previous prime is 21387227. The next prime is 21387251. The reversal of 21387229 is 92278312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21387229 - 2¹ = 21387227 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21387194 and 21387203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387227) 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, 103719 + ... + 103924.

It is an arithmetic number, because the mean of its divisors is an integer number (5398744).

Almost surely, 2^21387229 is an apocalyptic number.

It is an amenable number.

21387229 is a deficient number, since it is larger than the sum of its proper divisors (207747).

21387229 is a wasteful number, since it uses less digits than its factorization.

21387229 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207746.

The product of its digits is 12096, while the sum is 34.

The square root of 21387229 is about 4624.6328502920. The cubic root of 21387229 is about 277.5778706334.

The spelling of 21387229 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred twenty-nine".