21684473042281 has 27 divisors (see below), whose sum is σ = 25329158519301. Its totient is φ = 18510107765184.

The previous prime is 21684473042249. The next prime is 21684473042317. The reversal of 21684473042281 is 18224037448612.

The square root of 21684473042281 is 4656659.

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 1537984424025 + 20146488618256 = 1240155^2 + 4488484^2 .

It is not a de Polignac number, because 21684473042281 - 2⁵ = 21684473042249 is a prime.

It is a super-3 number, since 3×21684473042281³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21684473042201) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 8768487661 + ... + 8768490133.

Almost surely, 2^{21684473042281} is an apocalyptic number.

21684473042281 is the 4656659-th square number.

21684473042281 is the 2328330-th centered octagonal number.

It is an amenable number.

21684473042281 is a deficient number, since it is larger than the sum of its proper divisors (3644685477020).

21684473042281 is an frugal number, since it uses more digits than its factorization.

21684473042281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5498 (or 2749 counting only the distinct ones).

The product of its (nonzero) digits is 4128768, while the sum is 52.

The spelling of 21684473042281 in words is "twenty-one trillion, six hundred eighty-four billion, four hundred seventy-three million, forty-two thousand, two hundred eighty-one".