21660561633503 has 4 divisors (see below), whose sum is σ = 23326758682248. Its totient is φ = 19994364584760.

The previous prime is 21660561633413. The next prime is 21660561633527. The reversal of 21660561633503 is 30533616506612.

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 21660561633503 - 2⁸ = 21660561633247 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 (21660561633583) 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, 833098524353 + ... + 833098524378.

It is an arithmetic number, because the mean of its divisors is an integer number (5831689670562).

Almost surely, 2^{21660561633503} is an apocalyptic number.

21660561633503 is a deficient number, since it is larger than the sum of its proper divisors (1666197048745).

21660561633503 is a wasteful number, since it uses less digits than its factorization.

21660561633503 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1666197048744.

The product of its (nonzero) digits is 1749600, while the sum is 47.

The spelling of 21660561633503 in words is "twenty-one trillion, six hundred sixty billion, five hundred sixty-one million, six hundred thirty-three thousand, five hundred three".