13558040721 has 27 divisors (see below), whose sum is σ = 20146640241. Its totient is φ = 8786021184.

The previous prime is 13558040707. The next prime is 13558040723. The reversal of 13558040721 is 12704085531.

The square root of 13558040721 is 116439.

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

13558040721 is a `hidden beast` number, since 1 + 3 + 5 + 580 + 4 + 0 + 72 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 8718890625 + 4839150096 = 93375^2 + 69564^2 .

It is not a de Polignac number, because 13558040721 - 2¹⁹ = 13557516433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (13558040723) 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, 12924205 + ... + 12925253.

Almost surely, 2^13558040721 is an apocalyptic number.

13558040721 is the 116439-th square number.

13558040721 is the 58220-th centered octagonal number.

It is an amenable number.

13558040721 is a deficient number, since it is larger than the sum of its proper divisors (6588599520).

13558040721 is an frugal number, since it uses more digits than its factorization.

13558040721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2178 (or 1089 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

Multiplying 13558040721 by its sum of digits (36), we get a square (488089465956 = 698634²).

The spelling of 13558040721 in words is "thirteen billion, five hundred fifty-eight million, forty thousand, seven hundred twenty-one".