221501406 has 32 divisors (see below), whose sum is σ = 506914560. Its totient is φ = 63207936.

The previous prime is 221501387. The next prime is 221501429. The reversal of 221501406 is 604105122.

221501406 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (21).

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 15 ways as a sum of consecutive naturals, for example, 36990 + ... + 42558.

It is an arithmetic number, because the mean of its divisors is an integer number (15841080).

Almost surely, 2^221501406 is an apocalyptic number.

221501406 is an abundant number, since it is smaller than the sum of its proper divisors (285413154).

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

221501406 is a wasteful number, since it uses less digits than its factorization.

221501406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6528.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 221501406 is about 14882.9233015560. The cubic root of 221501406 is about 605.0512498988.

Adding to 221501406 its reverse (604105122), we get a palindrome (825606528).

The spelling of 221501406 in words is "two hundred twenty-one million, five hundred one thousand, four hundred six".