21919847 has 2 divisors, whose sum is σ = 21919848. Its totient is φ = 21919846.

The previous prime is 21919831. The next prime is 21919903. The reversal of 21919847 is 74891912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21919847 - 2⁴ = 21919831 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21916847) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10959923 + 10959924.

It is an arithmetic number, because the mean of its divisors is an integer number (10959924).

Almost surely, 2^21919847 is an apocalyptic number.

21919847 is a deficient number, since it is larger than the sum of its proper divisors (1).

21919847 is an equidigital number, since it uses as much as digits as its factorization.

21919847 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 41.

The square root of 21919847 is about 4681.8636246691. The cubic root of 21919847 is about 279.8632282700.

The spelling of 21919847 in words is "twenty-one million, nine hundred nineteen thousand, eight hundred forty-seven".