16216421 has 4 divisors (see below), whose sum is σ = 17463852. Its totient is φ = 14968992.

The previous prime is 16216399. The next prime is 16216427. The reversal of 16216421 is 12461261.

16216421 = T₁₅₇₃ + T₁₅₇₄ + ... + T₁₅₈₅.

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 7365796 + 8850625 = 2714^2 + 2975^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16216421 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16216427) 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, 623696 + ... + 623721.

It is an arithmetic number, because the mean of its divisors is an integer number (4365963).

Almost surely, 2^16216421 is an apocalyptic number.

It is an amenable number.

16216421 is a deficient number, since it is larger than the sum of its proper divisors (1247431).

16216421 is a wasteful number, since it uses less digits than its factorization.

16216421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1247430.

The product of its digits is 576, while the sum is 23.

The square root of 16216421 is about 4026.9617579510. The cubic root of 16216421 is about 253.1152645953.

Adding to 16216421 its reverse (12461261), we get a palindrome (28677682).

The spelling of 16216421 in words is "sixteen million, two hundred sixteen thousand, four hundred twenty-one".