21004906 has 16 divisors (see below), whose sum is σ = 34020000. Its totient is φ = 9669168.

The previous prime is 21004901. The next prime is 21004909. The reversal of 21004906 is 60940012.

It is not an unprimeable number, because it can be changed into a prime (21004901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12165 + ... + 13783.

It is an arithmetic number, because the mean of its divisors is an integer number (2126250).

Almost surely, 2^21004906 is an apocalyptic number.

21004906 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21004906 is a deficient number, since it is larger than the sum of its proper divisors (13015094).

21004906 is a wasteful number, since it uses less digits than its factorization.

21004906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2133.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21004906 is about 4583.1109521808. The cubic root of 21004906 is about 275.9139005399.

Adding to 21004906 its reverse (60940012), we get a palindrome (81944918).

The spelling of 21004906 in words is "twenty-one million, four thousand, nine hundred six".