21137288651761 has 4 divisors (see below), whose sum is σ = 21346568737524. Its totient is φ = 20928008566000.

The previous prime is 21137288651723. The next prime is 21137288651821. The reversal of 21137288651761 is 16715688273112.

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 11247873826225 + 9889414825536 = 3353785^2 + 3144744^2 .

It is a cyclic number.

It is not a de Polignac number, because 21137288651761 - 2³³ = 21128698717169 is a prime.

It is a super-2 number, since 2×21137288651761² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21137288651696 and 21137288651705.

It is not an unprimeable number, because it can be changed into a prime (21137288651711) 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, 104640042730 + ... + 104640042931.

It is an arithmetic number, because the mean of its divisors is an integer number (5336642184381).

Almost surely, 2^{21137288651761} is an apocalyptic number.

It is an amenable number.

21137288651761 is a deficient number, since it is larger than the sum of its proper divisors (209280085763).

21137288651761 is a wasteful number, since it uses less digits than its factorization.

21137288651761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209280085762.

The product of its digits is 6773760, while the sum is 58.

The spelling of 21137288651761 in words is "twenty-one trillion, one hundred thirty-seven billion, two hundred eighty-eight million, six hundred fifty-one thousand, seven hundred sixty-one".