21655605 has 16 divisors (see below), whose sum is σ = 35844480. Its totient is φ = 11151168.

The previous prime is 21655589. The next prime is 21655607. The reversal of 21655605 is 50655612.

It is not a de Polignac number, because 21655605 - 2⁴ = 21655589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655607) 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 15 ways as a sum of consecutive naturals, for example, 24457 + ... + 25326.

It is an arithmetic number, because the mean of its divisors is an integer number (2240280).

Almost surely, 2^21655605 is an apocalyptic number.

It is an amenable number.

21655605 is a deficient number, since it is larger than the sum of its proper divisors (14188875).

21655605 is a wasteful number, since it uses less digits than its factorization.

21655605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49820.

The product of its (nonzero) digits is 9000, while the sum is 30.

The square root of 21655605 is about 4653.5583159557. The cubic root of 21655605 is about 278.7341026011.

The spelling of 21655605 in words is "twenty-one million, six hundred fifty-five thousand, six hundred five".