21247643 has 8 divisors (see below), whose sum is σ = 22701120. Its totient is φ = 19827720.

The previous prime is 21247631. The next prime is 21247649. The reversal of 21247643 is 34674212.

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 21247643 - 2⁶ = 21247579 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21247649) 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, 7073 + ... + 9618.

It is an arithmetic number, because the mean of its divisors is an integer number (2837640).

Almost surely, 2^21247643 is an apocalyptic number.

21247643 is a deficient number, since it is larger than the sum of its proper divisors (1453477).

21247643 is a wasteful number, since it uses less digits than its factorization.

21247643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16777.

The product of its digits is 8064, while the sum is 29.

The square root of 21247643 is about 4609.5165690124. The cubic root of 21247643 is about 276.9726716948.

The spelling of 21247643 in words is "twenty-one million, two hundred forty-seven thousand, six hundred forty-three".