21012406 has 16 divisors (see below), whose sum is σ = 32174064. Its totient is φ = 10289664.

The previous prime is 21012401. The next prime is 21012413. The reversal of 21012406 is 60421012.

It is a self number, because there is not a number n which added to its sum of digits gives 21012406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30886 + ... + 31558.

It is an arithmetic number, because the mean of its divisors is an integer number (2010879).

Almost surely, 2^21012406 is an apocalyptic number.

21012406 is a deficient number, since it is larger than the sum of its proper divisors (11161658).

21012406 is a wasteful number, since it uses less digits than its factorization.

21012406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 975.

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 21012406 is about 4583.9291006734. The cubic root of 21012406 is about 275.9467358532.

Adding to 21012406 its reverse (60421012), we get a palindrome (81433418).

The spelling of 21012406 in words is "twenty-one million, twelve thousand, four hundred six".