21568763557 has 4 divisors (see below), whose sum is σ = 23529560256. Its totient is φ = 19607966860.

The previous prime is 21568763551. The next prime is 21568763581. The reversal of 21568763557 is 75536786512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21568763557 is a prime.

It is a super-2 number, since 2×21568763557² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21568763498 and 21568763507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21568763551) 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, 980398333 + ... + 980398354.

It is an arithmetic number, because the mean of its divisors is an integer number (5882390064).

Almost surely, 2^21568763557 is an apocalyptic number.

It is an amenable number.

21568763557 is a deficient number, since it is larger than the sum of its proper divisors (1960796699).

21568763557 is a wasteful number, since it uses less digits than its factorization.

21568763557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1960796698.

The product of its digits is 10584000, while the sum is 55.

The spelling of 21568763557 in words is "twenty-one billion, five hundred sixty-eight million, seven hundred sixty-three thousand, five hundred fifty-seven".