16421665 has 8 divisors (see below), whose sum is σ = 21221928. Its totient is φ = 12126720.

The previous prime is 16421623. The next prime is 16421683. The reversal of 16421665 is 56612461.

16421665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 613089 + 15808576 = 783^2 + 3976^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 16421665 - 2¹⁹ = 15897377 is a prime.

It is a nialpdrome in base 16.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126256 + ... + 126385.

It is an arithmetic number, because the mean of its divisors is an integer number (2652741).

Almost surely, 2^16421665 is an apocalyptic number.

It is an amenable number.

16421665 is a deficient number, since it is larger than the sum of its proper divisors (4800263).

16421665 is a wasteful number, since it uses less digits than its factorization.

16421665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 252659.

The product of its digits is 8640, while the sum is 31.

The square root of 16421665 is about 4052.3653586517. The cubic root of 16421665 is about 254.1786465135.

The spelling of 16421665 in words is "sixteen million, four hundred twenty-one thousand, six hundred sixty-five".