1216506661531 has 4 divisors (see below), whose sum is σ = 1390293327472. Its totient is φ = 1042719995592.

The previous prime is 1216506661523. The next prime is 1216506661589. The reversal of 1216506661531 is 1351666056121.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1216506661531 - 2³ = 1216506661523 is a prime.

It is a super-2 number, since 2×1216506661531² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1216506691531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 86893332960 + ... + 86893332973.

It is an arithmetic number, because the mean of its divisors is an integer number (347573331868).

Almost surely, 2^{1216506661531} is an apocalyptic number.

1216506661531 is a deficient number, since it is larger than the sum of its proper divisors (173786665941).

1216506661531 is an equidigital number, since it uses as much as digits as its factorization.

1216506661531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173786665940.

The product of its (nonzero) digits is 194400, while the sum is 43.

The spelling of 1216506661531 in words is "one trillion, two hundred sixteen billion, five hundred six million, six hundred sixty-one thousand, five hundred thirty-one".