21712147 has 4 divisors (see below), whose sum is σ = 21721536. Its totient is φ = 21702760.

The previous prime is 21712133. The next prime is 21712151. The reversal of 21712147 is 74121712.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21712147 - 2¹⁵ = 21679379 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21722147) 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, 1497 + ... + 6757.

It is an arithmetic number, because the mean of its divisors is an integer number (5430384).

Almost surely, 2^21712147 is an apocalyptic number.

21712147 is a deficient number, since it is larger than the sum of its proper divisors (9389).

21712147 is an equidigital number, since it uses as much as digits as its factorization.

21712147 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9388.

The product of its digits is 784, while the sum is 25.

The square root of 21712147 is about 4659.6294917085. The cubic root of 21712147 is about 278.9764799912.

Adding to 21712147 its reverse (74121712), we get a palindrome (95833859).

The spelling of 21712147 in words is "twenty-one million, seven hundred twelve thousand, one hundred forty-seven".