21055100561 has 8 divisors (see below), whose sum is σ = 23457907584. Its totient is φ = 18733744720.

The previous prime is 21055100557. The next prime is 21055100567. The reversal of 21055100561 is 16500155012.

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 21055100561 - 2² = 21055100557 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21055100561.

It is not an unprimeable number, because it can be changed into a prime (21055100567) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20362250 + ... + 20363283.

It is an arithmetic number, because the mean of its divisors is an integer number (2932238448).

Almost surely, 2^21055100561 is an apocalyptic number.

It is an amenable number.

21055100561 is a deficient number, since it is larger than the sum of its proper divisors (2402807023).

21055100561 is a wasteful number, since it uses less digits than its factorization.

21055100561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40725591.

The product of its (nonzero) digits is 1500, while the sum is 26.

Adding to 21055100561 its reverse (16500155012), we get a palindrome (37555255573).

The spelling of 21055100561 in words is "twenty-one billion, fifty-five million, one hundred thousand, five hundred sixty-one".