1218071721 has 8 divisors (see below), whose sum is σ = 1633484160. Its totient is φ = 807353552.

The previous prime is 1218071689. The next prime is 1218071731. The reversal of 1218071721 is 1271708121.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1218071721 - 2⁵ = 1218071689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1218071731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1172961 + ... + 1173998.

It is an arithmetic number, because the mean of its divisors is an integer number (204185520).

Almost surely, 2^1218071721 is an apocalyptic number.

It is an amenable number.

1218071721 is a deficient number, since it is larger than the sum of its proper divisors (415412439).

1218071721 is a wasteful number, since it uses less digits than its factorization.

1218071721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2347135.

The product of its (nonzero) digits is 1568, while the sum is 30.

The square root of 1218071721 is about 34900.8842438125. The cubic root of 1218071721 is about 1067.9664760690.

Adding to 1218071721 its reverse (1271708121), we get a palindrome (2489779842).

The spelling of 1218071721 in words is "one billion, two hundred eighteen million, seventy-one thousand, seven hundred twenty-one".