21018757057 has 2 divisors, whose sum is σ = 21018757058. Its totient is φ = 21018757056.

The previous prime is 21018757043. The next prime is 21018757091. The reversal of 21018757057 is 75075781012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21013111681 + 5645376 = 144959^2 + 2376^2 .

It is a cyclic number.

It is not a de Polignac number, because 21018757057 - 2¹⁵ = 21018724289 is a prime.

It is not a weakly prime, because it can be changed into another prime (21018757157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10509378528 + 10509378529.

It is an arithmetic number, because the mean of its divisors is an integer number (10509378529).

Almost surely, 2^21018757057 is an apocalyptic number.

It is an amenable number.

21018757057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21018757057 is an equidigital number, since it uses as much as digits as its factorization.

21018757057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 137200, while the sum is 43.

The spelling of 21018757057 in words is "twenty-one billion, eighteen million, seven hundred fifty-seven thousand, fifty-seven".