21018404 has 48 divisors (see below), whose sum is σ = 41997312. Its totient is φ = 9120000.

The previous prime is 21018401. The next prime is 21018407. The reversal of 21018404 is 40481012.

It is an interprime number because it is at equal distance from previous prime (21018401) and next prime (21018407).

It is not an unprimeable number, because it can be changed into a prime (21018401) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 109949 + ... + 110139.

It is an arithmetic number, because the mean of its divisors is an integer number (874944).

Almost surely, 2^21018404 is an apocalyptic number.

It is an amenable number.

21018404 is a deficient number, since it is larger than the sum of its proper divisors (20978908).

21018404 is a wasteful number, since it uses less digits than its factorization.

21018404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308 (or 306 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 21018404 is about 4584.5832962222. The cubic root of 21018404 is about 275.9729897253.

Adding to 21018404 its reverse (40481012), we get a palindrome (61499416).

It can be divided in two parts, 2101 and 8404, that multiplied together give a square (17656804 = 4202²).

The spelling of 21018404 in words is "twenty-one million, eighteen thousand, four hundred four".