221015720 has 32 divisors (see below), whose sum is σ = 503284320. Its totient is φ = 87339840.

The previous prime is 221015713. The next prime is 221015731. The reversal of 221015720 is 27510122.

221015720 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 = 221015692 and 221015701.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29966 + ... + 36605.

It is an arithmetic number, because the mean of its divisors is an integer number (15727635).

Almost surely, 2^221015720 is an apocalyptic number.

221015720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221015720 is an abundant number, since it is smaller than the sum of its proper divisors (282268600).

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

221015720 is a wasteful number, since it uses less digits than its factorization.

221015720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66665 (or 66661 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 221015720 is about 14866.5974587328. The cubic root of 221015720 is about 604.6086944399.

Adding to 221015720 its reverse (27510122), we get a palindrome (248525842).

The spelling of 221015720 in words is "two hundred twenty-one million, fifteen thousand, seven hundred twenty".