21673620 has 54 divisors (see below), whose sum is σ = 65933322. Its totient is φ = 5762976.

The previous prime is 21673577. The next prime is 21673633. The reversal of 21673620 is 2637612.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 17338896 + 4334724 = 4164^2 + 2082^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 62287 + ... + 62633.

Almost surely, 2^21673620 is an apocalyptic number.

21673620 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 21673620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32966661).

21673620 is an abundant number, since it is smaller than the sum of its proper divisors (44259702).

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

21673620 is a wasteful number, since it uses less digits than its factorization.

21673620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 709 (or 357 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 27.

The square root of 21673620 is about 4655.4935291546. The cubic root of 21673620 is about 278.8113728673.

The spelling of 21673620 in words is "twenty-one million, six hundred seventy-three thousand, six hundred twenty".