21016819 has 4 divisors (see below), whose sum is σ = 21029944. Its totient is φ = 21003696.

The previous prime is 21016817. The next prime is 21016829. The reversal of 21016819 is 91861012.

It is a happy number.

21016819 is an esthetic number in base 7, because in such base its adjacent digits differ by 1.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21016819 - 2¹ = 21016817 is a prime.

It is a super-2 number, since 2×21016819² = 883413361757522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21016813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3762 + ... + 7495.

It is an arithmetic number, because the mean of its divisors is an integer number (5257486).

Almost surely, 2^21016819 is an apocalyptic number.

21016819 is a deficient number, since it is larger than the sum of its proper divisors (13125).

21016819 is a wasteful number, since it uses less digits than its factorization.

21016819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13124.

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 21016819 is about 4584.4104310151. The cubic root of 21016819 is about 275.9660525005.

The spelling of 21016819 in words is "twenty-one million, sixteen thousand, eight hundred nineteen".