16431021 has 18 divisors (see below), whose sum is σ = 24263018. Its totient is φ = 10712160.

The previous prime is 16431017. The next prime is 16431043. The reversal of 16431021 is 12013461.

It is a happy number.

16431021 is a `hidden beast` number, since 1 + 643 + 1 + 0 + 21 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 4796100 + 11634921 = 2190^2 + 3411^2 .

It is not a de Polignac number, because 16431021 - 2² = 16431017 is a prime.

It is a super-2 number, since 2×16431021² = 539956902204882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 16430985 and 16431003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16431221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 94891 + ... + 95063.

Almost surely, 2^16431021 is an apocalyptic number.

It is an amenable number.

16431021 is a deficient number, since it is larger than the sum of its proper divisors (7831997).

16431021 is an equidigital number, since it uses as much as digits as its factorization.

16431021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 413 (or 237 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 16431021 is about 4053.5195817956. The cubic root of 16431021 is about 254.2269088533.

Adding to 16431021 its reverse (12013461), we get a palindrome (28444482).

The spelling of 16431021 in words is "sixteen million, four hundred thirty-one thousand, twenty-one".