21540527557 has 2 divisors, whose sum is σ = 21540527558. Its totient is φ = 21540527556.

The previous prime is 21540527549. The next prime is 21540527573. The reversal of 21540527557 is 75572504512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12622747201 + 8917780356 = 112351^2 + 94434^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540527557 - 2³ = 21540527549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21540527507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770263778 + 10770263779.

It is an arithmetic number, because the mean of its divisors is an integer number (10770263779).

Almost surely, 2^21540527557 is an apocalyptic number.

It is an amenable number.

21540527557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21540527557 is an equidigital number, since it uses as much as digits as its factorization.

21540527557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 490000, while the sum is 43.

The spelling of 21540527557 in words is "twenty-one billion, five hundred forty million, five hundred twenty-seven thousand, five hundred fifty-seven".