21778970929 has 9 divisors (see below), whose sum is σ = 23138112001. Its totient is φ = 20495493760.

The previous prime is 21778970923. The next prime is 21778971013. The reversal of 21778970929 is 92907987712.

The square root of 21778970929 is 147577.

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

It can be written as a sum of positive squares in 4 ways, for example, as 7937919025 + 13841051904 = 89095^2 + 117648^2 .

It is not a de Polignac number, because 21778970929 - 2⁵ = 21778970897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21778970923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2504469 + ... + 2513149.

Almost surely, 2^21778970929 is an apocalyptic number.

21778970929 is the 147577-th square number.

21778970929 is the 73789-th centered octagonal number.

It is an amenable number.

21778970929 is a deficient number, since it is larger than the sum of its proper divisors (1359141072).

21778970929 is an frugal number, since it uses more digits than its factorization.

21778970929 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17396 (or 8698 counting only the distinct ones).

The product of its (nonzero) digits is 8001504, while the sum is 61.

The spelling of 21778970929 in words is "twenty-one billion, seven hundred seventy-eight million, nine hundred seventy thousand, nine hundred twenty-nine".