21429247 has 4 divisors (see below), whose sum is σ = 24490576. Its totient is φ = 18367920.

The previous prime is 21429209. The next prime is 21429257. The reversal of 21429247 is 74292412.

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

It is a cyclic number.

It is not a de Polignac number, because 21429247 - 2¹¹ = 21427199 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21429257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1530654 + ... + 1530667.

It is an arithmetic number, because the mean of its divisors is an integer number (6122644).

Almost surely, 2^21429247 is an apocalyptic number.

21429247 is a deficient number, since it is larger than the sum of its proper divisors (3061329).

21429247 is an equidigital number, since it uses as much as digits as its factorization.

21429247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3061328.

The product of its digits is 8064, while the sum is 31.

The square root of 21429247 is about 4629.1734683418. The cubic root of 21429247 is about 277.7595310266.

The spelling of 21429247 in words is "twenty-one million, four hundred twenty-nine thousand, two hundred forty-seven".