21040806 has 8 divisors (see below), whose sum is σ = 42081624. Its totient is φ = 7013600.

The previous prime is 21040787. The next prime is 21040807. The reversal of 21040806 is 60804012.

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

21040806 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040807) 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, 1753395 + ... + 1753406.

It is an arithmetic number, because the mean of its divisors is an integer number (5260203).

Almost surely, 2^21040806 is an apocalyptic number.

21040806 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21040806 is a wasteful number, since it uses less digits than its factorization.

21040806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3506806.

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21040806 is about 4587.0258338056. The cubic root of 21040806 is about 276.0710014769.

Adding to 21040806 its reverse (60804012), we get a palindrome (81844818).

The spelling of 21040806 in words is "twenty-one million, forty thousand, eight hundred six".