21731447 has 2 divisors, whose sum is σ = 21731448. Its totient is φ = 21731446.

The previous prime is 21731441. The next prime is 21731449. The reversal of 21731447 is 74413712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21731447 - 2⁸ = 21731191 is a prime.

Together with 21731449, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21731441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865723 + 10865724.

It is an arithmetic number, because the mean of its divisors is an integer number (10865724).

Almost surely, 2^21731447 is an apocalyptic number.

21731447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731447 is an equidigital number, since it uses as much as digits as its factorization.

21731447 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4704, while the sum is 29.

The square root of 21731447 is about 4661.7000117983. The cubic root of 21731447 is about 279.0591165524.

The spelling of 21731447 in words is "twenty-one million, seven hundred thirty-one thousand, four hundred forty-seven".