21203312557 has 4 divisors (see below), whose sum is σ = 24232357216. Its totient is φ = 18174267900.

The previous prime is 21203312549. The next prime is 21203312567. The reversal of 21203312557 is 75521330212.

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 21203312557 - 2³ = 21203312549 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 (21203312567) 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 in 3 ways as a sum of consecutive naturals, for example, 1514522319 + ... + 1514522332.

It is an arithmetic number, because the mean of its divisors is an integer number (6058089304).

Almost surely, 2^21203312557 is an apocalyptic number.

It is an amenable number.

21203312557 is a deficient number, since it is larger than the sum of its proper divisors (3029044659).

21203312557 is an equidigital number, since it uses as much as digits as its factorization.

21203312557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3029044658.

The product of its (nonzero) digits is 12600, while the sum is 31.

Adding to 21203312557 its reverse (75521330212), we get a palindrome (96724642769).

The spelling of 21203312557 in words is "twenty-one billion, two hundred three million, three hundred twelve thousand, five hundred fifty-seven".