16221720 has 32 divisors (see below), whose sum is σ = 48665520. Its totient is φ = 4325760.

The previous prime is 16221713. The next prime is 16221727. The reversal of 16221720 is 2712261.

16221720 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (16221713) and next prime (16221727).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16221727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 67471 + ... + 67710.

Almost surely, 2^16221720 is an apocalyptic number.

16221720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

16221720 is an abundant number, since it is smaller than the sum of its proper divisors (32443800).

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

16221720 is a wasteful number, since it uses less digits than its factorization.

16221720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135195 (or 135191 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 16221720 is about 4027.6196444054. The cubic root of 16221720 is about 253.1428315437.

Adding to 16221720 its reverse (2712261), we get a palindrome (18933981).

The spelling of 16221720 in words is "sixteen million, two hundred twenty-one thousand, seven hundred twenty".