21709370281 has 3 divisors (see below), whose sum is σ = 21709517623. Its totient is φ = 21709222940.

The previous prime is 21709370261. The next prime is 21709370299. The reversal of 21709370281 is 18207390712.

It is a happy number.

The square root of 21709370281 is 147341.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 10963974681 + 10745395600 = 104709^2 + 103660^2 .

It is not a de Polignac number, because 21709370281 - 2⁹ = 21709369769 is a prime.

It is a super-2 number, since 2×21709370281² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21709370231) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 73671 + ... + 221011.

Almost surely, 2^21709370281 is an apocalyptic number.

21709370281 is the 147341-st square number.

21709370281 is the 73671-st centered octagonal number.

It is an amenable number.

21709370281 is a deficient number, since it is larger than the sum of its proper divisors (147342).

21709370281 is an frugal number, since it uses more digits than its factorization.

21709370281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 294682 (or 147341 counting only the distinct ones).

The product of its (nonzero) digits is 42336, while the sum is 40.

The spelling of 21709370281 in words is "twenty-one billion, seven hundred nine million, three hundred seventy thousand, two hundred eighty-one".