7218031681 has 27 divisors (see below), whose sum is σ = 8595433161. Its totient is φ = 6043643424.

The previous prime is 7218031663. The next prime is 7218031687. The reversal of 7218031681 is 1861308127.

The square root of 7218031681 is 84959.

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 3347201025 + 3870830656 = 57855^2 + 62216^2 .

It is not a de Polignac number, because 7218031681 - 2⁹ = 7218031169 is a prime.

It is a super-2 number, since 2×7218031681² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 7218031681.

It is not an unprimeable number, because it can be changed into a prime (7218031687) 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, 31519675 + ... + 31519903.

Almost surely, 2^7218031681 is an apocalyptic number.

7218031681 is the 84959-th square number.

7218031681 is the 42480-th centered octagonal number.

It is an amenable number.

7218031681 is a deficient number, since it is larger than the sum of its proper divisors (1377401480).

7218031681 is an frugal number, since it uses more digits than its factorization.

7218031681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 578 (or 289 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 37.

The cubic root of 7218031681 is about 1932.5894065644.

The spelling of 7218031681 in words is "seven billion, two hundred eighteen million, thirty-one thousand, six hundred eighty-one".