21311755557 has 4 divisors (see below), whose sum is σ = 28415674080. Its totient is φ = 14207837036.

The previous prime is 21311755547. The next prime is 21311755559. The reversal of 21311755557 is 75555711312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21311755557 - 2¹¹ = 21311753509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311755559) 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, 3551959257 + ... + 3551959262.

It is an arithmetic number, because the mean of its divisors is an integer number (7103918520).

Almost surely, 2^21311755557 is an apocalyptic number.

It is an amenable number.

21311755557 is a deficient number, since it is larger than the sum of its proper divisors (7103918523).

21311755557 is an equidigital number, since it uses as much as digits as its factorization.

21311755557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7103918522.

The product of its digits is 183750, while the sum is 42.

The spelling of 21311755557 in words is "twenty-one billion, three hundred eleven million, seven hundred fifty-five thousand, five hundred fifty-seven".