21821016 has 32 divisors (see below), whose sum is σ = 62346240. Its totient is φ = 6234528.

The previous prime is 21821003. The next prime is 21821027. The reversal of 21821016 is 61012812.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21820983 and 21821001.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 64776 + ... + 65111.

It is an arithmetic number, because the mean of its divisors is an integer number (1948320).

Almost surely, 2^21821016 is an apocalyptic number.

It is an amenable number.

21821016 is an abundant number, since it is smaller than the sum of its proper divisors (40525224).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21821016 is a wasteful number, since it uses less digits than its factorization.

21821016 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129903 (or 129899 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 21.

The square root of 21821016 is about 4671.2970361560. The cubic root of 21821016 is about 279.4419838984.

Adding to 21821016 its reverse (61012812), we get a palindrome (82833828).

The spelling of 21821016 in words is "twenty-one million, eight hundred twenty-one thousand, sixteen".