16155721 has 4 divisors (see below), whose sum is σ = 16226500. Its totient is φ = 16084944.

The previous prime is 16155677. The next prime is 16155731. The reversal of 16155721 is 12755161.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15515721 + 640000 = 3939^2 + 800^2 .

It is a cyclic number.

It is not a de Polignac number, because 16155721 - 2¹³ = 16147529 is a prime.

It is a super-2 number, since 2×16155721² = 522014642059682, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16155721.

It is not an unprimeable number, because it can be changed into a prime (16155731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35046 + ... + 35503.

It is an arithmetic number, because the mean of its divisors is an integer number (4056625).

Almost surely, 2^16155721 is an apocalyptic number.

It is an amenable number.

16155721 is a deficient number, since it is larger than the sum of its proper divisors (70779).

16155721 is an equidigital number, since it uses as much as digits as its factorization.

16155721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70778.

The product of its digits is 2100, while the sum is 28.

The square root of 16155721 is about 4019.4179926950. The cubic root of 16155721 is about 252.7990561790.

The spelling of 16155721 in words is "sixteen million, one hundred fifty-five thousand, seven hundred twenty-one".