21818241 has 21 divisors (see below), whose sum is σ = 32902579. Its totient is φ = 14461416.

The previous prime is 21818227. The next prime is 21818267. The reversal of 21818241 is 14281812.

The square root of 21818241 is 4671.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 19847025 + 1971216 = 4455^2 + 1404^2 .

It is not a de Polignac number, because 21818241 - 2¹⁹ = 21293953 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21818201) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 126031 + ... + 126203.

Almost surely, 2^21818241 is an apocalyptic number.

21818241 is the 4671-st square number.

21818241 is the 2336-th centered octagonal number.

It is an amenable number.

21818241 is a deficient number, since it is larger than the sum of its proper divisors (11084338).

21818241 is an frugal number, since it uses more digits than its factorization.

21818241 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364 (or 176 counting only the distinct ones).

The product of its digits is 1024, while the sum is 27.

The cubic root of 21818241 is about 279.4301377592.

Multiplying 21818241 by its product of digits (1024), we get a square (22341878784 = 149472²).

The spelling of 21818241 in words is "twenty-one million, eight hundred eighteen thousand, two hundred forty-one".