16040021 has 4 divisors (see below), whose sum is σ = 16048032. Its totient is φ = 16032012.

The previous prime is 16039963. The next prime is 16040053. The reversal of 16040021 is 12004061.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12004061 = 109 ⋅110129.

It is a cyclic number.

It is not a de Polignac number, because 16040021 - 2⁶ = 16039957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16039978 and 16040005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16040221) 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, 2000 + ... + 6006.

It is an arithmetic number, because the mean of its divisors is an integer number (4012008).

Almost surely, 2^16040021 is an apocalyptic number.

It is an amenable number.

16040021 is a deficient number, since it is larger than the sum of its proper divisors (8011).

16040021 is an equidigital number, since it uses as much as digits as its factorization.

16040021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8010.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 16040021 is about 4004.9995006242. Note that the first 3 decimals coincide. The cubic root of 16040021 is about 252.1941321339.

Adding to 16040021 its reverse (12004061), we get a palindrome (28044082).

The spelling of 16040021 in words is "sixteen million, forty thousand, twenty-one".