21471522732721 has 4 divisors (see below), whose sum is σ = 21471842654500. Its totient is φ = 21471202810944.

The previous prime is 21471522732691. The next prime is 21471522732749. The reversal of 21471522732721 is 12723722517412.

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 10714073911696 + 10757448821025 = 3273236^2 + 3279855^2 .

It is a cyclic number.

It is not a de Polignac number, because 21471522732721 - 2¹⁷ = 21471522601649 is a prime.

It is a super-2 number, since 2×21471522732721² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21471522732521) 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, 159860196 + ... + 159994453.

It is an arithmetic number, because the mean of its divisors is an integer number (5367960663625).

Almost surely, 2^{21471522732721} is an apocalyptic number.

It is an amenable number.

21471522732721 is a deficient number, since it is larger than the sum of its proper divisors (319921779).

21471522732721 is an equidigital number, since it uses as much as digits as its factorization.

21471522732721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319921778.

The product of its digits is 658560, while the sum is 46.

The spelling of 21471522732721 in words is "twenty-one trillion, four hundred seventy-one billion, five hundred twenty-two million, seven hundred thirty-two thousand, seven hundred twenty-one".