21403247 has 4 divisors (see below), whose sum is σ = 22141320. Its totient is φ = 20665176.

The previous prime is 21403243. The next prime is 21403259. The reversal of 21403247 is 74230412.

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 21403247 - 2² = 21403243 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 (21403241) 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, 368993 + ... + 369050.

It is an arithmetic number, because the mean of its divisors is an integer number (5535330).

Almost surely, 2^21403247 is an apocalyptic number.

21403247 is a deficient number, since it is larger than the sum of its proper divisors (738073).

21403247 is an equidigital number, since it uses as much as digits as its factorization.

21403247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738072.

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21403247 is about 4626.3643393058. The cubic root of 21403247 is about 277.6471508066.

Adding to 21403247 its reverse (74230412), we get a palindrome (95633659).

The spelling of 21403247 in words is "twenty-one million, four hundred three thousand, two hundred forty-seven".