21504006 has 12 divisors (see below), whose sum is σ = 46592052. Its totient is φ = 7167996.

The previous prime is 21503981. The next prime is 21504017. The reversal of 21504006 is 60040512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18), and also a Moran number because the ratio is a prime number: 1194667 = 21504006 / (2 + 1 + 5 + 0 + 4 + 0 + 0 + 6).

It is a self number, because there is not a number n which added to its sum of digits gives 21504006.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 597316 + ... + 597351.

It is an arithmetic number, because the mean of its divisors is an integer number (3882671).

Almost surely, 2^21504006 is an apocalyptic number.

21504006 is an abundant number, since it is smaller than the sum of its proper divisors (25088046).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21504006 is a wasteful number, since it uses less digits than its factorization.

21504006 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1194675 (or 1194672 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21504006 is about 4637.2412057170. The cubic root of 21504006 is about 278.0821574542.

Adding to 21504006 its reverse (60040512), we get a palindrome (81544518).

The spelling of 21504006 in words is "twenty-one million, five hundred four thousand, six".