21811249 has 8 divisors (see below), whose sum is σ = 22346280. Its totient is φ = 21280896.

The previous prime is 21811211. The next prime is 21811261. The reversal of 21811249 is 94211812.

It can be written as a sum of positive squares in 4 ways, for example, as 16321600 + 5489649 = 4040^2 + 2343^2 .

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 21811249 - 2⁷ = 21811121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21811849) 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, 9397 + ... + 11485.

It is an arithmetic number, because the mean of its divisors is an integer number (2793285).

Almost surely, 2^21811249 is an apocalyptic number.

It is an amenable number.

21811249 is a deficient number, since it is larger than the sum of its proper divisors (535031).

21811249 is a wasteful number, since it uses less digits than its factorization.

21811249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2339.

The product of its digits is 1152, while the sum is 28.

The square root of 21811249 is about 4670.2514921576. The cubic root of 21811249 is about 279.4002853028.

The spelling of 21811249 in words is "twenty-one million, eight hundred eleven thousand, two hundred forty-nine".