21418813 has 4 divisors (see below), whose sum is σ = 23066428. Its totient is φ = 19771200.

The previous prime is 21418807. The next prime is 21418823. The reversal of 21418813 is 31881412.

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 8191044 + 13227769 = 2862^2 + 3637^2 .

It is a cyclic number.

It is not a de Polignac number, because 21418813 - 2¹⁷ = 21287741 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 (21418823) 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, 823788 + ... + 823813.

It is an arithmetic number, because the mean of its divisors is an integer number (5766607).

Almost surely, 2^21418813 is an apocalyptic number.

It is an amenable number.

21418813 is a deficient number, since it is larger than the sum of its proper divisors (1647615).

21418813 is a wasteful number, since it uses less digits than its factorization.

21418813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1647614.

The product of its digits is 1536, while the sum is 28.

The square root of 21418813 is about 4628.0463480825. The cubic root of 21418813 is about 277.7144429056.

The spelling of 21418813 in words is "twenty-one million, four hundred eighteen thousand, eight hundred thirteen".