16621813 has 4 divisors (see below), whose sum is σ = 17900428. Its totient is φ = 15343200.

The previous prime is 16621811. The next prime is 16621841. The reversal of 16621813 is 31812661.

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 1435204 + 15186609 = 1198^2 + 3897^2 .

It is a cyclic number.

It is not a de Polignac number, because 16621813 - 2¹ = 16621811 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16621811) 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, 639288 + ... + 639313.

It is an arithmetic number, because the mean of its divisors is an integer number (4475107).

Almost surely, 2^16621813 is an apocalyptic number.

16621813 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

16621813 is a deficient number, since it is larger than the sum of its proper divisors (1278615).

16621813 is a wasteful number, since it uses less digits than its factorization.

16621813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1278614.

The product of its digits is 1728, while the sum is 28.

The square root of 16621813 is about 4076.9857738285. The cubic root of 16621813 is about 255.2071263442.

The spelling of 16621813 in words is "sixteen million, six hundred twenty-one thousand, eight hundred thirteen".