21221305406 has 8 divisors (see below), whose sum is σ = 36379380720. Its totient is φ = 9094845168.

The previous prime is 21221305381. The next prime is 21221305421. The reversal of 21221305406 is 60450312212.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 757903751 + ... + 757903778.

It is an arithmetic number, because the mean of its divisors is an integer number (4547422590).

Almost surely, 2^21221305406 is an apocalyptic number.

21221305406 is a deficient number, since it is larger than the sum of its proper divisors (15158075314).

21221305406 is a wasteful number, since it uses less digits than its factorization.

21221305406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1515807538.

The product of its (nonzero) digits is 2880, while the sum is 26.

Adding to 21221305406 its reverse (60450312212), we get a palindrome (81671617618).

The spelling of 21221305406 in words is "twenty-one billion, two hundred twenty-one million, three hundred five thousand, four hundred six".