21006117757 has 4 divisors (see below), whose sum is σ = 21073661856. Its totient is φ = 20938573660.

The previous prime is 21006117751. The next prime is 21006117791. The reversal of 21006117757 is 75771160012.

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 21006117757 - 2³ = 21006117749 is a prime.

It is a super-2 number, since 2×21006117757² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006117751) 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, 33771583 + ... + 33772204.

It is an arithmetic number, because the mean of its divisors is an integer number (5268415464).

Almost surely, 2^21006117757 is an apocalyptic number.

It is an amenable number.

21006117757 is a deficient number, since it is larger than the sum of its proper divisors (67544099).

21006117757 is an equidigital number, since it uses as much as digits as its factorization.

21006117757 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67544098.

The product of its (nonzero) digits is 20580, while the sum is 37.

Adding to 21006117757 its reverse (75771160012), we get a palindrome (96777277769).

The spelling of 21006117757 in words is "twenty-one billion, six million, one hundred seventeen thousand, seven hundred fifty-seven".