21101307857 has 4 divisors (see below), whose sum is σ = 24115780416. Its totient is φ = 18086835300.

The previous prime is 21101307839. The next prime is 21101307889. The reversal of 21101307857 is 75870310112.

It is a happy number.

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 21101307857 - 2¹² = 21101303761 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21101307257) 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, 1507236269 + ... + 1507236282.

It is an arithmetic number, because the mean of its divisors is an integer number (6028945104).

Almost surely, 2^21101307857 is an apocalyptic number.

It is an amenable number.

21101307857 is a deficient number, since it is larger than the sum of its proper divisors (3014472559).

21101307857 is an equidigital number, since it uses as much as digits as its factorization.

21101307857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3014472558.

The product of its (nonzero) digits is 11760, while the sum is 35.

Adding to 21101307857 its reverse (75870310112), we get a palindrome (96971617969).

The spelling of 21101307857 in words is "twenty-one billion, one hundred one million, three hundred seven thousand, eight hundred fifty-seven".