21684747 has 8 divisors (see below), whose sum is σ = 33043456. Its totient is φ = 12391272.

The previous prime is 21684739. The next prime is 21684763. The reversal of 21684747 is 74748612.

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

It is not a de Polignac number, because 21684747 - 2³ = 21684739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21684797) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 516283 + ... + 516324.

It is an arithmetic number, because the mean of its divisors is an integer number (4130432).

Almost surely, 2^21684747 is an apocalyptic number.

21684747 is a deficient number, since it is larger than the sum of its proper divisors (11358709).

21684747 is a wasteful number, since it uses less digits than its factorization.

21684747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1032617.

The product of its digits is 75264, while the sum is 39.

The square root of 21684747 is about 4656.6884156018. The cubic root of 21684747 is about 278.8590776100.

The spelling of 21684747 in words is "twenty-one million, six hundred eighty-four thousand, seven hundred forty-seven".