21815042 has 8 divisors (see below), whose sum is σ = 33023100. Its totient is φ = 10807344.

The previous prime is 21815039. The next prime is 21815051. The reversal of 21815042 is 24051812.

It can be written as a sum of positive squares in 2 ways, for example, as 19989841 + 1825201 = 4471^2 + 1351^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21814999 and 21815017.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 49817 + ... + 50252.

Almost surely, 2^21815042 is an apocalyptic number.

21815042 is a deficient number, since it is larger than the sum of its proper divisors (11208058).

21815042 is a wasteful number, since it uses less digits than its factorization.

21815042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100180.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21815042 is about 4670.6575554198. The cubic root of 21815042 is about 279.4164803688.

Adding to 21815042 its reverse (24051812), we get a palindrome (45866854).

The spelling of 21815042 in words is "twenty-one million, eight hundred fifteen thousand, forty-two".