21721574791 has 8 divisors (see below), whose sum is σ = 25625452544. Its totient is φ = 18017895960.

The previous prime is 21721574789. The next prime is 21721574807. The reversal of 21721574791 is 19747512712.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21721574791 - 2¹ = 21721574789 is a prime.

It is a super-2 number, since 2×21721574791² (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 (21721574701) 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 7 ways as a sum of consecutive naturals, for example, 50049495 + ... + 50049928.

It is an arithmetic number, because the mean of its divisors is an integer number (3203181568).

Almost surely, 2^21721574791 is an apocalyptic number.

21721574791 is a deficient number, since it is larger than the sum of its proper divisors (3903877753).

21721574791 is a wasteful number, since it uses less digits than its factorization.

21721574791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100099461.

The product of its digits is 246960, while the sum is 46.

The spelling of 21721574791 in words is "twenty-one billion, seven hundred twenty-one million, five hundred seventy-four thousand, seven hundred ninety-one".