16020721 has 4 divisors (see below), whose sum is σ = 16179444. Its totient is φ = 15862000.

The previous prime is 16020713. The next prime is 16020733. The reversal of 16020721 is 12702061.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12702061 = 67 ⋅189583.

It can be written as a sum of positive squares in 2 ways, for example, as 8381025 + 7639696 = 2895^2 + 2764^2 .

It is a cyclic number.

It is not a de Polignac number, because 16020721 - 2³ = 16020713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16020761) 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, 79210 + ... + 79411.

It is an arithmetic number, because the mean of its divisors is an integer number (4044861).

Almost surely, 2^16020721 is an apocalyptic number.

It is an amenable number.

16020721 is a deficient number, since it is larger than the sum of its proper divisors (158723).

16020721 is a wasteful number, since it uses less digits than its factorization.

16020721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158722.

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 16020721 is about 4002.5892869491. The cubic root of 16020721 is about 252.0929414881.

Adding to 16020721 its reverse (12702061), we get a palindrome (28722782).

The spelling of 16020721 in words is "sixteen million, twenty thousand, seven hundred twenty-one".