21655044166621 has 4 divisors (see below), whose sum is σ = 21853714296700. Its totient is φ = 21456374036544.

The previous prime is 21655044166573. The next prime is 21655044166669. The reversal of 21655044166621 is 12666144055612.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21655044166573) and next prime (21655044166669).

It can be written as a sum of positive squares in 2 ways, for example, as 18757171212025 + 2897872954596 = 4330955^2 + 1702314^2 .

It is a cyclic number.

It is not a de Polignac number, because 21655044166621 - 2⁷ = 21655044166493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655044166121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99335064876 + ... + 99335065093.

It is an arithmetic number, because the mean of its divisors is an integer number (5463428574175).

Almost surely, 2^{21655044166621} is an apocalyptic number.

It is an amenable number.

21655044166621 is a deficient number, since it is larger than the sum of its proper divisors (198670130079).

21655044166621 is a wasteful number, since it uses less digits than its factorization.

21655044166621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198670130078.

The product of its (nonzero) digits is 2073600, while the sum is 49.

The spelling of 21655044166621 in words is "twenty-one trillion, six hundred fifty-five billion, forty-four million, one hundred sixty-six thousand, six hundred twenty-one".