21285819655 has 4 divisors (see below), whose sum is σ = 25542983592. Its totient is φ = 17028655720.

The previous prime is 21285819619. The next prime is 21285819671. The reversal of 21285819655 is 55691858212.

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

It is a de Polignac number, because none of the positive numbers 2^k-21285819655 is a prime.

It is a super-2 number, since 2×21285819655² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2128581961 + ... + 2128581970.

It is an arithmetic number, because the mean of its divisors is an integer number (6385745898).

Almost surely, 2^21285819655 is an apocalyptic number.

21285819655 is a deficient number, since it is larger than the sum of its proper divisors (4257163937).

21285819655 is an equidigital number, since it uses as much as digits as its factorization.

21285819655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4257163936.

The product of its digits is 1728000, while the sum is 52.

The spelling of 21285819655 in words is "twenty-one billion, two hundred eighty-five million, eight hundred nineteen thousand, six hundred fifty-five".