21821649 has 8 divisors (see below), whose sum is σ = 29155392. Its totient is φ = 14517840.

The previous prime is 21821647. The next prime is 21821651. The reversal of 21821649 is 94612812.

It is an interprime number because it is at equal distance from previous prime (21821647) and next prime (21821651).

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

It is not a de Polignac number, because 21821649 - 2¹ = 21821647 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21821647) 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, 5722 + ... + 8739.

It is an arithmetic number, because the mean of its divisors is an integer number (3644424).

Almost surely, 2^21821649 is an apocalyptic number.

It is an amenable number.

21821649 is a deficient number, since it is larger than the sum of its proper divisors (7333743).

21821649 is a wasteful number, since it uses less digits than its factorization.

21821649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14967.

The product of its digits is 6912, while the sum is 33.

The square root of 21821649 is about 4671.3647898660. The cubic root of 21821649 is about 279.4446859581. Note that the first 3 decimals are identical.

The spelling of 21821649 in words is "twenty-one million, eight hundred twenty-one thousand, six hundred forty-nine".