21531658171 has 2 divisors, whose sum is σ = 21531658172. Its totient is φ = 21531658170.

The previous prime is 21531658157. The next prime is 21531658199. The reversal of 21531658171 is 17185613512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21531658171 - 2⁵ = 21531658139 is a prime.

It is a super-2 number, since 2×21531658171² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21531658151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765829085 + 10765829086.

It is an arithmetic number, because the mean of its divisors is an integer number (10765829086).

Almost surely, 2^21531658171 is an apocalyptic number.

21531658171 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531658171 is an equidigital number, since it uses as much as digits as its factorization.

21531658171 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 50400, while the sum is 40.

The spelling of 21531658171 in words is "twenty-one billion, five hundred thirty-one million, six hundred fifty-eight thousand, one hundred seventy-one".