21019817 has 16 divisors (see below), whose sum is σ = 26138112. Its totient is φ = 16459200.

The previous prime is 21019799. The next prime is 21019841. The reversal of 21019817 is 71891012.

It is a cyclic number.

It is not a de Polignac number, because 21019817 - 2¹⁸ = 20757673 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21019817.

It is not an unprimeable number, because it can be changed into a prime (21016817) 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 15 ways as a sum of consecutive naturals, for example, 8048 + ... + 10334.

It is an arithmetic number, because the mean of its divisors is an integer number (1633632).

Almost surely, 2^21019817 is an apocalyptic number.

It is an amenable number.

21019817 is a deficient number, since it is larger than the sum of its proper divisors (5118295).

21019817 is a wasteful number, since it uses less digits than its factorization.

21019817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2408.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 21019817 is about 4584.7373970599. The cubic root of 21019817 is about 275.9791738469.

The spelling of 21019817 in words is "twenty-one million, nineteen thousand, eight hundred seventeen".