21505757655 has 8 divisors (see below), whose sum is σ = 34409212272. Its totient is φ = 11469737408.

The previous prime is 21505757633. The next prime is 21505757717. The reversal of 21505757655 is 55675750512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21505757655 - 2⁶ = 21505757591 is a prime.

It is a super-2 number, since 2×21505757655² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 716858574 + ... + 716858603.

It is an arithmetic number, because the mean of its divisors is an integer number (4301151534).

Almost surely, 2^21505757655 is an apocalyptic number.

21505757655 is a deficient number, since it is larger than the sum of its proper divisors (12903454617).

21505757655 is a wasteful number, since it uses less digits than its factorization.

21505757655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1433717185.

The product of its (nonzero) digits is 1837500, while the sum is 48.

The spelling of 21505757655 in words is "twenty-one billion, five hundred five million, seven hundred fifty-seven thousand, six hundred fifty-five".