21409847 has 2 divisors, whose sum is σ = 21409848. Its totient is φ = 21409846.

The previous prime is 21409823. The next prime is 21409867. The reversal of 21409847 is 74890412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21409847 - 2¹⁰ = 21408823 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21409807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704923 + 10704924.

It is an arithmetic number, because the mean of its divisors is an integer number (10704924).

Almost surely, 2^21409847 is an apocalyptic number.

21409847 is a deficient number, since it is larger than the sum of its proper divisors (1).

21409847 is an equidigital number, since it uses as much as digits as its factorization.

21409847 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21409847 is about 4627.0775874195. The cubic root of 21409847 is about 277.6756867085.

The spelling of 21409847 in words is "twenty-one million, four hundred nine thousand, eight hundred forty-seven".