16220721 has 8 divisors (see below), whose sum is σ = 23593824. Its totient is φ = 9830720.

The previous prime is 16220713. The next prime is 16220759. The reversal of 16220721 is 12702261.

16220721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 16220721 - 2³ = 16220713 is a prime.

It is a super-2 number, since 2×16220721² = 526223579519682, which contains 22 as substring.

It is a Curzon number.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (16220791) 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, 245736 + ... + 245801.

It is an arithmetic number, because the mean of its divisors is an integer number (2949228).

Almost surely, 2^16220721 is an apocalyptic number.

16220721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16220721 is a deficient number, since it is larger than the sum of its proper divisors (7373103).

16220721 is a wasteful number, since it uses less digits than its factorization.

16220721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 491551.

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

The square root of 16220721 is about 4027.4956238337. The cubic root of 16220721 is about 253.1376349127.

Adding to 16220721 its reverse (12702261), we get a palindrome (28922982).

The spelling of 16220721 in words is "sixteen million, two hundred twenty thousand, seven hundred twenty-one".