21115515506357 has 2 divisors, whose sum is σ = 21115515506358. Its totient is φ = 21115515506356.

The previous prime is 21115515506347. The next prime is 21115515506359. The reversal of 21115515506357 is 75360551551112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19488701989201 + 1626813517156 = 4414601^2 + 1275466^2 .

It is a cyclic number.

It is not a de Polignac number, because 21115515506357 - 2¹² = 21115515502261 is a prime.

It is a super-2 number, since 2×21115515506357² (a number of 27 digits) contains 22 as substring.

Together with 21115515506359, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21115515506359) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557757753178 + 10557757753179.

It is an arithmetic number, because the mean of its divisors is an integer number (10557757753179).

Almost surely, 2^{21115515506357} is an apocalyptic number.

It is an amenable number.

21115515506357 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115515506357 is an equidigital number, since it uses as much as digits as its factorization.

21115515506357 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 787500, while the sum is 47.

The spelling of 21115515506357 in words is "twenty-one trillion, one hundred fifteen billion, five hundred fifteen million, five hundred six thousand, three hundred fifty-seven".