21447971 has 2 divisors, whose sum is σ = 21447972. Its totient is φ = 21447970.

The previous prime is 21447953. The next prime is 21447991. The reversal of 21447971 is 17974412.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21447971 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21447991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10723985 + 10723986.

It is an arithmetic number, because the mean of its divisors is an integer number (10723986).

Almost surely, 2^21447971 is an apocalyptic number.

21447971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21447971 is an equidigital number, since it uses as much as digits as its factorization.

21447971 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14112, while the sum is 35.

The square root of 21447971 is about 4631.1954180319. The cubic root of 21447971 is about 277.8404057840.

The spelling of 21447971 in words is "twenty-one million, four hundred forty-seven thousand, nine hundred seventy-one".