1216390615801 has 3 divisors (see below), whose sum is σ = 1216391718703. Its totient is φ = 1216389512900.

The previous prime is 1216390615747. The next prime is 1216390615807. The reversal of 1216390615801 is 1085160936121.

The square root of 1216390615801 is 1102901.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1205386605801 + 11004010000 = 1097901^2 + 104900^2 .

It is not a de Polignac number, because 1216390615801 - 2¹⁹ = 1216390091513 is a prime.

It is a super-2 number, since 2×1216390615801² (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 (1216390615807) by changing a digit.

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 2 ways as a sum of consecutive naturals, for example, 551451 + ... + 1654351.

Almost surely, 2^{1216390615801} is an apocalyptic number.

1216390615801 is the 1102901-st square number.

1216390615801 is the 551451-st centered octagonal number.

It is an amenable number.

1216390615801 is a deficient number, since it is larger than the sum of its proper divisors (1102902).

1216390615801 is an frugal number, since it uses more digits than its factorization.

1216390615801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2205802 (or 1102901 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 43.

The spelling of 1216390615801 in words is "one trillion, two hundred sixteen billion, three hundred ninety million, six hundred fifteen thousand, eight hundred one".