1851398356921 has 9 divisors (see below), whose sum is σ = 1863947323749. Its totient is φ = 1838933341500.

The previous prime is 1851398356897. The next prime is 1851398357023. The reversal of 1851398356921 is 1296538931581.

The square root of 1851398356921 is 1360661.

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

It is not a de Polignac number, because 1851398356921 - 2⁷ = 1851398356793 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1851398356921.

It is not an unprimeable number, because it can be changed into a prime (1851398356121) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 205455306 + ... + 205464316.

Almost surely, 2^{1851398356921} is an apocalyptic number.

1851398356921 is the 1360661-st square number.

1851398356921 is the 680331-st centered octagonal number.

It is an amenable number.

1851398356921 is a deficient number, since it is larger than the sum of its proper divisors (12548966828).

1851398356921 is an frugal number, since it uses more digits than its factorization.

1851398356921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18324 (or 9162 counting only the distinct ones).

The product of its digits is 13996800, while the sum is 61.

The spelling of 1851398356921 in words is "one trillion, eight hundred fifty-one billion, three hundred ninety-eight million, three hundred fifty-six thousand, nine hundred twenty-one".