21399447 has 8 divisors (see below), whose sum is σ = 30211056. Its totient is φ = 13427072.

The previous prime is 21399437. The next prime is 21399457. The reversal of 21399447 is 74499312.

It is an interprime number because it is at equal distance from previous prime (21399437) and next prime (21399457).

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

It is a cyclic number.

It is not a de Polignac number, because 21399447 - 2⁷ = 21399319 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21399437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 209748 + ... + 209849.

It is an arithmetic number, because the mean of its divisors is an integer number (3776382).

Almost surely, 2^21399447 is an apocalyptic number.

21399447 is a deficient number, since it is larger than the sum of its proper divisors (8811609).

21399447 is a wasteful number, since it uses less digits than its factorization.

21399447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419617.

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

The square root of 21399447 is about 4625.9536314148. The cubic root of 21399447 is about 277.6307183836.

The spelling of 21399447 in words is "twenty-one million, three hundred ninety-nine thousand, four hundred forty-seven".