21055100557 has 2 divisors, whose sum is σ = 21055100558. Its totient is φ = 21055100556.

The previous prime is 21055100537. The next prime is 21055100567. The reversal of 21055100557 is 75500155012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15486806916 + 5568293641 = 124446^2 + 74621^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21055100557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21055100537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10527550278 + 10527550279.

It is an arithmetic number, because the mean of its divisors is an integer number (10527550279).

Almost surely, 2^21055100557 is an apocalyptic number.

It is an amenable number.

21055100557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21055100557 is an equidigital number, since it uses as much as digits as its factorization.

21055100557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8750, while the sum is 31.

Adding to 21055100557 its reverse (75500155012), we get a palindrome (96555255569).

The spelling of 21055100557 in words is "twenty-one billion, fifty-five million, one hundred thousand, five hundred fifty-seven".