1816939547721 has 15 divisors (see below), whose sum is σ = 2714211767773. Its totient is φ = 1211284944180.

The previous prime is 1816939547669. The next prime is 1816939547749. The reversal of 1816939547721 is 1277459396181.

The square root of 1816939547721 is 1347939.

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

1816939547721 is a `hidden beast` number, since 1 + 8 + 1 + 69 + 3 + 9 + 547 + 7 + 21 = 666.

It is not a de Polignac number, because 1816939547721 - 2³¹ = 1814792064073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1816939547021) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 12056566 + ... + 12206336.

Almost surely, 2^{1816939547721} is an apocalyptic number.

1816939547721 is the 1347939-th square number.

1816939547721 is the 673970-th centered octagonal number.

It is an amenable number.

1816939547721 is a deficient number, since it is larger than the sum of its proper divisors (897272220052).

1816939547721 is an frugal number, since it uses more digits than its factorization.

1816939547721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 299554 (or 149774 counting only the distinct ones).

The product of its digits is 22861440, while the sum is 63.

The spelling of 1816939547721 in words is "one trillion, eight hundred sixteen billion, nine hundred thirty-nine million, five hundred forty-seven thousand, seven hundred twenty-one".