221321720 has 16 divisors (see below), whose sum is σ = 497973960. Its totient is φ = 88528672.

The previous prime is 221321713. The next prime is 221321743. The reversal of 221321720 is 27123122.

221321720 is digitally balanced in base 2, 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 (20).

It is a junction number, because it is equal to n+sod(n) for n = 221321692 and 221321701.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2766482 + ... + 2766561.

Almost surely, 2^221321720 is an apocalyptic number.

221321720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221321720 is an abundant number, since it is smaller than the sum of its proper divisors (276652240).

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

221321720 is a wasteful number, since it uses less digits than its factorization.

221321720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5533054 (or 5533050 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 221321720 is about 14876.8854267283. The cubic root of 221321720 is about 604.8875960836.

Adding to 221321720 its reverse (27123122), we get a palindrome (248444842).

The spelling of 221321720 in words is "two hundred twenty-one million, three hundred twenty-one thousand, seven hundred twenty".