21724427 has 2 divisors, whose sum is σ = 21724428. Its totient is φ = 21724426.

The previous prime is 21724421. The next prime is 21724433. The reversal of 21724427 is 72442712.

It is a balanced prime because it is at equal distance from previous prime (21724421) and next prime (21724433).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21724427 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21724427.

It is not a weakly prime, because it can be changed into another prime (21724421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10862213 + 10862214.

It is an arithmetic number, because the mean of its divisors is an integer number (10862214).

Almost surely, 2^21724427 is an apocalyptic number.

21724427 is a deficient number, since it is larger than the sum of its proper divisors (1).

21724427 is an equidigital number, since it uses as much as digits as its factorization.

21724427 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6272, while the sum is 29.

The square root of 21724427 is about 4660.9470067788. The cubic root of 21724427 is about 279.0290647727.

The spelling of 21724427 in words is "twenty-one million, seven hundred twenty-four thousand, four hundred twenty-seven".