21506868 has 36 divisors (see below), whose sum is σ = 54582528. Its totient is φ = 7140240.

The previous prime is 21506867. The next prime is 21506869. The reversal of 21506868 is 86860512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21506867) and next prime (21506869).

It is a tau number, because it is divible by the number of its divisors (36).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506861) 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, 9133 + ... + 11243.

Almost surely, 2^21506868 is an apocalyptic number.

It is an amenable number.

21506868 is an abundant number, since it is smaller than the sum of its proper divisors (33075660).

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

21506868 is a wasteful number, since it uses less digits than its factorization.

21506868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2404 (or 2399 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 21506868 is about 4637.5497840994. The cubic root of 21506868 is about 278.0944936956.

The spelling of 21506868 in words is "twenty-one million, five hundred six thousand, eight hundred sixty-eight".