221206451 has 4 divisors (see below), whose sum is σ = 221732304. Its totient is φ = 220680600.

The previous prime is 221206409. The next prime is 221206457. The reversal of 221206451 is 154602122.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221206451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221206457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262295 + ... + 263136.

It is an arithmetic number, because the mean of its divisors is an integer number (55433076).

Almost surely, 2^221206451 is an apocalyptic number.

221206451 is a deficient number, since it is larger than the sum of its proper divisors (525853).

221206451 is an equidigital number, since it uses as much as digits as its factorization.

221206451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 525852.

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 221206451 is about 14873.0108249809. The cubic root of 221206451 is about 604.7825651261.

Adding to 221206451 its reverse (154602122), we get a palindrome (375808573).

The spelling of 221206451 in words is "two hundred twenty-one million, two hundred six thousand, four hundred fifty-one".