21316747 has 4 divisors (see below), whose sum is σ = 22004416. Its totient is φ = 20629080.

The previous prime is 21316741. The next prime is 21316751. The reversal of 21316747 is 74761312.

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 21316747 - 2³ = 21316739 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 687637 = 21316747 / (2 + 1 + 3 + 1 + 6 + 7 + 4 + 7).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21316741) 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, 343788 + ... + 343849.

It is an arithmetic number, because the mean of its divisors is an integer number (5501104).

Almost surely, 2^21316747 is an apocalyptic number.

21316747 is a deficient number, since it is larger than the sum of its proper divisors (687669).

21316747 is an equidigital number, since it uses as much as digits as its factorization.

21316747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 687668.

The product of its digits is 7056, while the sum is 31.

The square root of 21316747 is about 4617.0062811307. The cubic root of 21316747 is about 277.2726140968.

The spelling of 21316747 in words is "twenty-one million, three hundred sixteen thousand, seven hundred forty-seven".