21821976 has 96 divisors (see below), whose sum is σ = 65707200. Its totient is φ = 6486720.

The previous prime is 21821953. The next prime is 21821977. The reversal of 21821976 is 67912812.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21821976.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821977) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 46495 + ... + 46961.

It is an arithmetic number, because the mean of its divisors is an integer number (684450).

Almost surely, 2^21821976 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21821976, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32853600).

21821976 is an abundant number, since it is smaller than the sum of its proper divisors (43885224).

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

21821976 is a wasteful number, since it uses less digits than its factorization.

21821976 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 549 (or 542 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21821976 is about 4671.3997902128. The cubic root of 21821976 is about 279.4460817884.

The spelling of 21821976 in words is "twenty-one million, eight hundred twenty-one thousand, nine hundred seventy-six".