21440247 has 8 divisors (see below), whose sum is σ = 30268656. Its totient is φ = 13452672.

The previous prime is 21440239. The next prime is 21440257. The reversal of 21440247 is 74204412.

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

It is not a de Polignac number, because 21440247 - 2³ = 21440239 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21440207) 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, 210148 + ... + 210249.

It is an arithmetic number, because the mean of its divisors is an integer number (3783582).

Almost surely, 2^21440247 is an apocalyptic number.

21440247 is a deficient number, since it is larger than the sum of its proper divisors (8828409).

21440247 is a wasteful number, since it uses less digits than its factorization.

21440247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420417.

The product of its (nonzero) digits is 1792, while the sum is 24.

The square root of 21440247 is about 4630.3614329769. The cubic root of 21440247 is about 277.8070491406.

Adding to 21440247 its reverse (74204412), we get a palindrome (95644659).

The spelling of 21440247 in words is "twenty-one million, four hundred forty thousand, two hundred forty-seven".