221642406 has 20 divisors (see below), whose sum is σ = 496643532. Its totient is φ = 73880748.

The previous prime is 221642387. The next prime is 221642431. The reversal of 221642406 is 604246122.

221642406 is a `hidden beast` number, since 2 + 216 + 42 + 406 = 666.

It is a super-2 number, since 2×221642406² = 98250712274937672, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 221642406.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 683920 + ... + 684243.

Almost surely, 2^221642406 is an apocalyptic number.

221642406 is an abundant number, since it is smaller than the sum of its proper divisors (275001126).

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

221642406 is a wasteful number, since it uses less digits than its factorization.

221642406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1368177 (or 1368168 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 27.

The square root of 221642406 is about 14887.6595205559. The cubic root of 221642406 is about 605.1796074443.

Adding to 221642406 its reverse (604246122), we get a palindrome (825888528).

The spelling of 221642406 in words is "two hundred twenty-one million, six hundred forty-two thousand, four hundred six".