7218891409 has 4 divisors (see below), whose sum is σ = 7219277604. Its totient is φ = 7218505216.

The previous prime is 7218891397. The next prime is 7218891419. The reversal of 7218891409 is 9041988127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9041988127 = 10067 ⋅898181.

It can be written as a sum of positive squares in 2 ways, for example, as 4465580625 + 2753310784 = 66825^2 + 52472^2 .

It is a cyclic number.

It is not a de Polignac number, because 7218891409 - 2⁵ = 7218891377 is a prime.

It is a super-2 number, since 2×7218891409² (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 (7218891419) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 163552 + ... + 202945.

It is an arithmetic number, because the mean of its divisors is an integer number (1804819401).

Almost surely, 2^7218891409 is an apocalyptic number.

It is an amenable number.

7218891409 is a deficient number, since it is larger than the sum of its proper divisors (386195).

7218891409 is a wasteful number, since it uses less digits than its factorization.

7218891409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386194.

The product of its (nonzero) digits is 290304, while the sum is 49.

The square root of 7218891409 is about 84964.0595134201. The cubic root of 7218891409 is about 1932.6661327107. Note that the first 3 decimals are identical.

The spelling of 7218891409 in words is "seven billion, two hundred eighteen million, eight hundred ninety-one thousand, four hundred nine".