21821811 has 8 divisors (see below), whose sum is σ = 31740864. Its totient is φ = 13225320.

The previous prime is 21821797. The next prime is 21821819. The reversal of 21821811 is 11812812.

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

It is not a de Polignac number, because 21821811 - 2¹³ = 21813619 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21821819) 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, 330601 + ... + 330666.

It is an arithmetic number, because the mean of its divisors is an integer number (3967608).

Almost surely, 2^21821811 is an apocalyptic number.

21821811 is a deficient number, since it is larger than the sum of its proper divisors (9919053).

21821811 is a wasteful number, since it uses less digits than its factorization.

21821811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 661281.

The product of its digits is 256, while the sum is 24.

The square root of 21821811 is about 4671.3821295201. The cubic root of 21821811 is about 279.4453774721.

It can be divided in two parts, 2182 and 1811, that added together give a palindrome (3993).

The spelling of 21821811 in words is "twenty-one million, eight hundred twenty-one thousand, eight hundred eleven".