21447427 has 2 divisors, whose sum is σ = 21447428. Its totient is φ = 21447426.

The previous prime is 21447407. The next prime is 21447509. The reversal of 21447427 is 72474412.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21447427 is a prime.

It is a Chen prime.

It is equal to p_1356466 and since 21447427 and 1356466 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21447407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10723713 + 10723714.

It is an arithmetic number, because the mean of its divisors is an integer number (10723714).

Almost surely, 2^21447427 is an apocalyptic number.

21447427 is a deficient number, since it is larger than the sum of its proper divisors (1).

21447427 is an equidigital number, since it uses as much as digits as its factorization.

21447427 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12544, while the sum is 31.

The square root of 21447427 is about 4631.1366855233. The cubic root of 21447427 is about 277.8380567434.

The spelling of 21447427 in words is "twenty-one million, four hundred forty-seven thousand, four hundred twenty-seven".