1661212155015 has 48 divisors (see below), whose sum is σ = 3463981248000. Its totient is φ = 719442254016.

The previous prime is 1661212154993. The next prime is 1661212155067. The reversal of 1661212155015 is 5105512121661.

1661212155015 is a `hidden beast` number, since 1 + 6 + 6 + 121 + 21 + 5 + 501 + 5 = 666.

It is not a de Polignac number, because 1661212155015 - 2¹⁵ = 1661212122247 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 138775315 + ... + 138787284.

It is an arithmetic number, because the mean of its divisors is an integer number (72166276000).

Almost surely, 2^{1661212155015} is an apocalyptic number.

1661212155015 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1661212155015 is an abundant number, since it is smaller than the sum of its proper divisors (1802769092985).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1661212155015 is a wasteful number, since it uses less digits than its factorization.

1661212155015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 277562636 (or 277562633 counting only the distinct ones).

The product of its (nonzero) digits is 18000, while the sum is 36.

Adding to 1661212155015 its reverse (5105512121661), we get a palindrome (6766724276676).

The spelling of 1661212155015 in words is "one trillion, six hundred sixty-one billion, two hundred twelve million, one hundred fifty-five thousand, fifteen".