21758905081 has 9 divisors (see below), whose sum is σ = 23116795149. Its totient is φ = 20476609344.

The previous prime is 21758905067. The next prime is 21758905111. The reversal of 21758905081 is 18050985712.

The square root of 21758905081 is 147509.

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 49829481 + 21709075600 = 7059^2 + 147340^2 .

It is not a de Polignac number, because 21758905081 - 2¹³ = 21758896889 is a prime.

It is a super-2 number, since 2×21758905081² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21758905681) 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, 2503315 + ... + 2511991.

Almost surely, 2^21758905081 is an apocalyptic number.

21758905081 is the 147509-th square number.

21758905081 is the 73755-th centered octagonal number.

It is an amenable number.

21758905081 is a deficient number, since it is larger than the sum of its proper divisors (1357890068).

21758905081 is an frugal number, since it uses more digits than its factorization.

21758905081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17388 (or 8694 counting only the distinct ones).

The product of its (nonzero) digits is 201600, while the sum is 46.

The spelling of 21758905081 in words is "twenty-one billion, seven hundred fifty-eight million, nine hundred five thousand, eighty-one".