21709295851 has 4 divisors (see below), whose sum is σ = 22986313272. Its totient is φ = 20432278432.

The previous prime is 21709295849. The next prime is 21709295873. The reversal of 21709295851 is 15859290712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21709295851 - 2¹ = 21709295849 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21709295795 and 21709295804.

It is not an unprimeable number, because it can be changed into a prime (21709290851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 638508685 + ... + 638508718.

It is an arithmetic number, because the mean of its divisors is an integer number (5746578318).

Almost surely, 2^21709295851 is an apocalyptic number.

21709295851 is a deficient number, since it is larger than the sum of its proper divisors (1277017421).

21709295851 is a wasteful number, since it uses less digits than its factorization.

21709295851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1277017420.

The product of its (nonzero) digits is 453600, while the sum is 49.

The spelling of 21709295851 in words is "twenty-one billion, seven hundred nine million, two hundred ninety-five thousand, eight hundred fifty-one".