21990847 has 4 divisors (see below), whose sum is σ = 23148280. Its totient is φ = 20833416.

The previous prime is 21990823. The next prime is 21990851. The reversal of 21990847 is 74809912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21990847 - 2¹⁹ = 21466559 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21990887) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 578688 + ... + 578725.

It is an arithmetic number, because the mean of its divisors is an integer number (5787070).

Almost surely, 2^21990847 is an apocalyptic number.

21990847 is a deficient number, since it is larger than the sum of its proper divisors (1157433).

21990847 is a wasteful number, since it uses less digits than its factorization.

21990847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1157432.

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 21990847 is about 4689.4399452387. The cubic root of 21990847 is about 280.1650684843.

The spelling of 21990847 in words is "twenty-one million, nine hundred ninety thousand, eight hundred forty-seven".