21421620 has 144 divisors (see below), whose sum is σ = 73382400. Its totient is φ = 5011200.

The previous prime is 21421619. The next prime is 21421627. The reversal of 21421620 is 2612412.

21421620 is a `hidden beast` number, since 2 + 1 + 42 + 1 + 620 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21421593 and 21421602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21421627) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 61206 + ... + 61554.

It is an arithmetic number, because the mean of its divisors is an integer number (509600).

Almost surely, 2^21421620 is an apocalyptic number.

21421620 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 21421620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36691200).

21421620 is an abundant number, since it is smaller than the sum of its proper divisors (51960780).

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

21421620 is a wasteful number, since it uses less digits than its factorization.

21421620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406 (or 401 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21421620 is about 4628.3495978588. The cubic root of 21421620 is about 277.7265741472.

The spelling of 21421620 in words is "twenty-one million, four hundred twenty-one thousand, six hundred twenty".