218251781956 has 24 divisors (see below), whose sum is σ = 411334723800. Its totient is φ = 100728148992.

The previous prime is 218251781939. The next prime is 218251781981. The reversal of 218251781956 is 659187152812.

It can be written as a sum of positive squares in 4 ways, for example, as 22371184900 + 195880597056 = 149570^2 + 442584^2 .

It is a hoax number, since the sum of its digits (55) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 218251781897 and 218251781906.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2078100 + ... + 2180596.

It is an arithmetic number, because the mean of its divisors is an integer number (17138946825).

Almost surely, 2^218251781956 is an apocalyptic number.

218251781956 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

218251781956 is a deficient number, since it is larger than the sum of its proper divisors (193082941844).

218251781956 is a wasteful number, since it uses less digits than its factorization.

218251781956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143463 (or 143461 counting only the distinct ones).

The product of its digits is 2419200, while the sum is 55.

The spelling of 218251781956 in words is "two hundred eighteen billion, two hundred fifty-one million, seven hundred eighty-one thousand, nine hundred fifty-six".