16406021 has 4 divisors (see below), whose sum is σ = 16496844. Its totient is φ = 16315200.

The previous prime is 16406017. The next prime is 16406023. The reversal of 16406021 is 12060461.

It is a happy number.

16406021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12060461 = 7 ⋅1722923.

It can be written as a sum of positive squares in 2 ways, for example, as 6076225 + 10329796 = 2465^2 + 3214^2 .

It is a cyclic number.

It is not a de Polignac number, because 16406021 - 2² = 16406017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16405984 and 16406002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16406023) 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, 45140 + ... + 45501.

It is an arithmetic number, because the mean of its divisors is an integer number (4124211).

Almost surely, 2^16406021 is an apocalyptic number.

It is an amenable number.

16406021 is a deficient number, since it is larger than the sum of its proper divisors (90823).

16406021 is an equidigital number, since it uses as much as digits as its factorization.

16406021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90822.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 16406021 is about 4050.4346680326. The cubic root of 16406021 is about 254.0979069518.

Adding to 16406021 its reverse (12060461), we get a palindrome (28466482).

The spelling of 16406021 in words is "sixteen million, four hundred six thousand, twenty-one".