21506976 has 72 divisors (see below), whose sum is σ = 62358660. Its totient is φ = 7028736.

The previous prime is 21506971. The next prime is 21506981. The reversal of 21506976 is 67960512.

It is an interprime number because it is at equal distance from previous prime (21506971) and next prime (21506981).

It can be written as a sum of positive squares in 2 ways, for example, as 20466576 + 1040400 = 4524^2 + 1020^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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 21506976.

It is not an unprimeable number, because it can be changed into a prime (21506971) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14560 + ... + 15968.

Almost surely, 2^21506976 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 21506976, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31179330).

21506976 is an abundant number, since it is smaller than the sum of its proper divisors (40851684).

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

21506976 is a wasteful number, since it uses less digits than its factorization.

21506976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1478 (or 1467 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 21506976 is about 4637.5614281646. The cubic root of 21506976 is about 278.0949591928.

The spelling of 21506976 in words is "twenty-one million, five hundred six thousand, nine hundred seventy-six".