20016821 has 4 divisors (see below), whose sum is σ = 21836544. Its totient is φ = 18197100.

The previous prime is 20016791. The next prime is 20016827. The reversal of 20016821 is 12861002.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20016821 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20016793 and 20016802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20016827) 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, 909845 + ... + 909866.

It is an arithmetic number, because the mean of its divisors is an integer number (5459136).

Almost surely, 2^20016821 is an apocalyptic number.

It is an amenable number.

20016821 is a deficient number, since it is larger than the sum of its proper divisors (1819723).

20016821 is a wasteful number, since it uses less digits than its factorization.

20016821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1819722.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 20016821 is about 4474.0162047091. The cubic root of 20016821 is about 271.5178390331.

Adding to 20016821 its reverse (12861002), we get a palindrome (32877823).

The spelling of 20016821 in words is "twenty million, sixteen thousand, eight hundred twenty-one".