21018413 has 4 divisors (see below), whose sum is σ = 22635228. Its totient is φ = 19401600.

The previous prime is 21018407. The next prime is 21018461. The reversal of 21018413 is 31481012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1684804 + 19333609 = 1298^2 + 4397^2 .

It is a cyclic number.

It is not a de Polignac number, because 21018413 - 2⁴ = 21018397 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 (21011413) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 808388 + ... + 808413.

It is an arithmetic number, because the mean of its divisors is an integer number (5658807).

Almost surely, 2^21018413 is an apocalyptic number.

It is an amenable number.

21018413 is a deficient number, since it is larger than the sum of its proper divisors (1616815).

21018413 is a wasteful number, since it uses less digits than its factorization.

21018413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1616814.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21018413 is about 4584.5842777726. The cubic root of 21018413 is about 275.9730291155.

Adding to 21018413 its reverse (31481012), we get a palindrome (52499425).

The spelling of 21018413 in words is "twenty-one million, eighteen thousand, four hundred thirteen".