21169920 has 144 divisors (see below), whose sum is σ = 69904800. Its totient is φ = 5455872.

The previous prime is 21169919. The next prime is 21169921. The reversal of 21169920 is 2996112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21169919) and next prime (21169921).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21169921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 142006 + ... + 142154.

It is an arithmetic number, because the mean of its divisors is an integer number (485450).

Almost surely, 2^21169920 is an apocalyptic number.

21169920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21169920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34952400).

21169920 is an abundant number, since it is smaller than the sum of its proper divisors (48734880).

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

21169920 is a wasteful number, since it uses less digits than its factorization.

21169920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 21169920 is about 4601.0781345246. The cubic root of 21169920 is about 276.6345408739.

The spelling of 21169920 in words is "twenty-one million, one hundred sixty-nine thousand, nine hundred twenty".