21506766 has 8 divisors (see below), whose sum is σ = 43013544. Its totient is φ = 7168920.

The previous prime is 21506753. The next prime is 21506843. The reversal of 21506766 is 66760512.

It is a sphenic number, since it is the product of 3 distinct primes.

21506766 is an admirable number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1792225 + ... + 1792236.

It is an arithmetic number, because the mean of its divisors is an integer number (5376693).

Almost surely, 2^21506766 is an apocalyptic number.

21506766 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21506766 is a wasteful number, since it uses less digits than its factorization.

21506766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3584466.

The product of its (nonzero) digits is 15120, while the sum is 33.

The square root of 21506766 is about 4637.5387868998. The cubic root of 21506766 is about 278.0940540580.

The spelling of 21506766 in words is "twenty-one million, five hundred six thousand, seven hundred sixty-six".