21168820 has 24 divisors (see below), whose sum is σ = 44541000. Its totient is φ = 8451072.

The previous prime is 21168817. The next prime is 21168821. The reversal of 21168820 is 2886112.

It can be written as a sum of positive squares in 4 ways, for example, as 4177936 + 16990884 = 2044^2 + 4122^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21168821) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19656 + ... + 20704.

It is an arithmetic number, because the mean of its divisors is an integer number (1855875).

Almost surely, 2^21168820 is an apocalyptic number.

21168820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21168820 is an abundant number, since it is smaller than the sum of its proper divisors (23372180).

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

21168820 is a wasteful number, since it uses less digits than its factorization.

21168820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2067 (or 2065 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 21168820 is about 4600.9585957711. The cubic root of 21168820 is about 276.6297494329.

The spelling of 21168820 in words is "twenty-one million, one hundred sixty-eight thousand, eight hundred twenty".