1243155681 has 28 divisors (see below), whose sum is σ = 1944945408. Its totient is φ = 792726264.

The previous prime is 1243155679. The next prime is 1243155689. The reversal of 1243155681 is 1865513421.

1243155681 is a `hidden beast` number, since 1 + 24 + 3 + 1 + 556 + 81 = 666.

It is not a de Polignac number, because 1243155681 - 2¹ = 1243155679 is a prime.

It is a super-2 number, since 2×1243155681² = 3090872094405147522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1243155689) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 20305 + ... + 53838.

It is an arithmetic number, because the mean of its divisors is an integer number (69462336).

Almost surely, 2^1243155681 is an apocalyptic number.

It is an amenable number.

1243155681 is a deficient number, since it is larger than the sum of its proper divisors (701789727).

1243155681 is an frugal number, since it uses more digits than its factorization.

1243155681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74184 (or 74169 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

The square root of 1243155681 is about 35258.4129109635. The cubic root of 1243155681 is about 1075.2476605522.

The spelling of 1243155681 in words is "one billion, two hundred forty-three million, one hundred fifty-five thousand, six hundred eighty-one".