21821901 has 16 divisors (see below), whose sum is σ = 29623104. Its totient is φ = 14287104.

The previous prime is 21821893. The next prime is 21821911. The reversal of 21821901 is 10912812.

It is not a de Polignac number, because 21821901 - 2³ = 21821893 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50181 + ... + 50613.

It is an arithmetic number, because the mean of its divisors is an integer number (1851444).

Almost surely, 2^21821901 is an apocalyptic number.

It is an amenable number.

21821901 is a deficient number, since it is larger than the sum of its proper divisors (7801203).

21821901 is a wasteful number, since it uses less digits than its factorization.

21821901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 700.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 21821901 is about 4671.3917626335. The cubic root of 21821901 is about 279.4457616451.

It can be divided in two parts, 21821 and 901, that added together give a palindrome (22722).

The spelling of 21821901 in words is "twenty-one million, eight hundred twenty-one thousand, nine hundred one".