1231789495561 has 16 divisors (see below), whose sum is σ = 1261390402944. Its totient is φ = 1202431170304.

The previous prime is 1231789495549. The next prime is 1231789495583. The reversal of 1231789495561 is 1655949871321.

It is a cyclic number.

It is not a de Polignac number, because 1231789495561 - 2²¹ = 1231787398409 is a prime.

It is a super-2 number, since 2×1231789495561² (a number of 25 digits) contains 22 as substring.

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 1231789495561.

It is not an unprimeable number, because it can be changed into a prime (1231789415561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18651180 + ... + 18717106.

It is an arithmetic number, because the mean of its divisors is an integer number (78836900184).

Almost surely, 2^{1231789495561} is an apocalyptic number.

It is an amenable number.

1231789495561 is a deficient number, since it is larger than the sum of its proper divisors (29600907383).

1231789495561 is a wasteful number, since it uses less digits than its factorization.

1231789495561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67760.

The product of its digits is 16329600, while the sum is 61.

The spelling of 1231789495561 in words is "one trillion, two hundred thirty-one billion, seven hundred eighty-nine million, four hundred ninety-five thousand, five hundred sixty-one".