21087683682557 has 4 divisors (see below), whose sum is σ = 21169736926716. Its totient is φ = 21005630438400.

The previous prime is 21087683682493. The next prime is 21087683682563. The reversal of 21087683682557 is 75528638678012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20466268369156 + 621415313401 = 4523966^2 + 788299^2 .

It is a cyclic number.

It is not a de Polignac number, because 21087683682557 - 2⁶ = 21087683682493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21087683682577) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41026621694 + ... + 41026622207.

It is an arithmetic number, because the mean of its divisors is an integer number (5292434231679).

Almost surely, 2^{21087683682557} is an apocalyptic number.

It is an amenable number.

21087683682557 is a deficient number, since it is larger than the sum of its proper divisors (82053244159).

21087683682557 is an equidigital number, since it uses as much as digits as its factorization.

21087683682557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82053244158.

The product of its (nonzero) digits is 270950400, while the sum is 68.

The spelling of 21087683682557 in words is "twenty-one trillion, eighty-seven billion, six hundred eighty-three million, six hundred eighty-two thousand, five hundred fifty-seven".