21571678129 has 9 divisors (see below), whose sum is σ = 21712559169. Its totient is φ = 21431708160.

The previous prime is 21571678111. The next prime is 21571678147. The reversal of 21571678129 is 92187617512.

The square root of 21571678129 is 146873.

It is a perfect power (a square), and thus also a powerful number.

It is an interprime number because it is at equal distance from previous prime (21571678111) and next prime (21571678147).

It can be written as a sum of positive squares in 4 ways, for example, as 15369800625 + 6201877504 = 123975^2 + 78752^2 .

It is not a de Polignac number, because 21571678129 - 2¹⁹ = 21571153841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21571678109) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 28346109 + ... + 28346869.

Almost surely, 2^21571678129 is an apocalyptic number.

21571678129 is the 146873-rd square number.

21571678129 is the 73437-th centered octagonal number.

It is an amenable number.

21571678129 is a deficient number, since it is larger than the sum of its proper divisors (140881040).

21571678129 is an frugal number, since it uses more digits than its factorization.

21571678129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1908 (or 954 counting only the distinct ones).

The product of its digits is 423360, while the sum is 49.

Multiplying 21571678129 by its sum of digits (49), we get a square (1057012228321 = 1028111²).

The spelling of 21571678129 in words is "twenty-one billion, five hundred seventy-one million, six hundred seventy-eight thousand, one hundred twenty-nine".