21447993 has 8 divisors (see below), whose sum is σ = 32682688. Its totient is φ = 12255984.

The previous prime is 21447991. The next prime is 21448003. The reversal of 21447993 is 39974412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21447993 - 2¹ = 21447991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21447991) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 510646 + ... + 510687.

It is an arithmetic number, because the mean of its divisors is an integer number (4085336).

Almost surely, 2^21447993 is an apocalyptic number.

It is an amenable number.

21447993 is a deficient number, since it is larger than the sum of its proper divisors (11234695).

21447993 is a wasteful number, since it uses less digits than its factorization.

21447993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1021343.

The product of its digits is 54432, while the sum is 39.

The square root of 21447993 is about 4631.1977932280. The cubic root of 21447993 is about 277.8405007811.

The spelling of 21447993 in words is "twenty-one million, four hundred forty-seven thousand, nine hundred ninety-three".