1216862771561 has 8 divisors (see below), whose sum is σ = 1288460833704. Its totient is φ = 1145266698240.

The previous prime is 1216862771533. The next prime is 1216862771591. The reversal of 1216862771561 is 1651772686121.

It can be written as a sum of positive squares in 4 ways, for example, as 431476883161 + 785385888400 = 656869^2 + 886220^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1216862771561 is a prime.

It is a super-2 number, since 2×1216862771561² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1216862771591) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 869921 + ... + 1786193.

It is an arithmetic number, because the mean of its divisors is an integer number (161057604213).

Almost surely, 2^{1216862771561} is an apocalyptic number.

It is an amenable number.

1216862771561 is a deficient number, since it is larger than the sum of its proper divisors (71598062143).

1216862771561 is an equidigital number, since it uses as much as digits as its factorization.

1216862771561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 994411.

The product of its digits is 1693440, while the sum is 53.

The spelling of 1216862771561 in words is "one trillion, two hundred sixteen billion, eight hundred sixty-two million, seven hundred seventy-one thousand, five hundred sixty-one".