21505266750518 has 4 divisors (see below), whose sum is σ = 32257900125780. Its totient is φ = 10752633375258.

The previous prime is 21505266750491. The next prime is 21505266750523. The reversal of 21505266750518 is 81505766250512.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21505266750518.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5376316687628 + ... + 5376316687631.

It is an arithmetic number, because the mean of its divisors is an integer number (8064475031445).

Almost surely, 2^{21505266750518} is an apocalyptic number.

21505266750518 is a deficient number, since it is larger than the sum of its proper divisors (10752633375262).

21505266750518 is a wasteful number, since it uses less digits than its factorization.

21505266750518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10752633375261.

The product of its (nonzero) digits is 5040000, while the sum is 53.

The spelling of 21505266750518 in words is "twenty-one trillion, five hundred five billion, two hundred sixty-six million, seven hundred fifty thousand, five hundred eighteen".