21801247 has 4 divisors (see below), whose sum is σ = 23478280. Its totient is φ = 20124216.

The previous prime is 21801211. The next prime is 21801271. The reversal of 21801247 is 74210812.

It is a happy number.

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 21801247 - 2¹¹ = 21799199 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 (21801347) 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 3 ways as a sum of consecutive naturals, for example, 838497 + ... + 838522.

It is an arithmetic number, because the mean of its divisors is an integer number (5869570).

Almost surely, 2^21801247 is an apocalyptic number.

21801247 is a deficient number, since it is larger than the sum of its proper divisors (1677033).

21801247 is a wasteful number, since it uses less digits than its factorization.

21801247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1677032.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21801247 is about 4669.1805490900. The cubic root of 21801247 is about 279.3575705102.

The spelling of 21801247 in words is "twenty-one million, eight hundred one thousand, two hundred forty-seven".