21663561255403 has 4 divisors (see below), whose sum is σ = 21663767894328. Its totient is φ = 21663354616480.

The previous prime is 21663561255377. The next prime is 21663561255431. The reversal of 21663561255403 is 30455216536612.

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

It is a cyclic number.

It is not a de Polignac number, because 21663561255403 - 2⁹ = 21663561254891 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21663561255433) 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, 103162126 + ... + 103371907.

It is an arithmetic number, because the mean of its divisors is an integer number (5415941973582).

Almost surely, 2^{21663561255403} is an apocalyptic number.

21663561255403 is a deficient number, since it is larger than the sum of its proper divisors (206638925).

21663561255403 is a wasteful number, since it uses less digits than its factorization.

21663561255403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206638924.

The product of its (nonzero) digits is 3888000, while the sum is 49.

The spelling of 21663561255403 in words is "twenty-one trillion, six hundred sixty-three billion, five hundred sixty-one million, two hundred fifty-five thousand, four hundred three".