21655761 has 8 divisors (see below), whose sum is σ = 28910784. Its totient is φ = 14418960.

The previous prime is 21655759. The next prime is 21655787. The reversal of 21655761 is 16755612.

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

It is not a de Polignac number, because 21655761 - 2¹ = 21655759 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21653761) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 1485 + ... + 6746.

It is an arithmetic number, because the mean of its divisors is an integer number (3613848).

Almost surely, 2^21655761 is an apocalyptic number.

It is an amenable number.

21655761 is a deficient number, since it is larger than the sum of its proper divisors (7255023).

21655761 is an equidigital number, since it uses as much as digits as its factorization.

21655761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9111.

The product of its digits is 12600, while the sum is 33.

The square root of 21655761 is about 4653.5750772927. The cubic root of 21655761 is about 278.7347719030.

The spelling of 21655761 in words is "twenty-one million, six hundred fifty-five thousand, seven hundred sixty-one".