1216551401 has 8 divisors (see below), whose sum is σ = 1317886920. Its totient is φ = 1122968496.

The previous prime is 1216551377. The next prime is 1216551403. The reversal of 1216551401 is 1041556121.

It can be written as a sum of positive squares in 4 ways, for example, as 545689600 + 670861801 = 23360^2 + 25901^2 .

It is not a de Polignac number, because 1216551401 - 2³⁰ = 142809577 is a prime.

It is a super-2 number, since 2×1216551401² = 2959994622550125602, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216551403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 274670 + ... + 279063.

It is an arithmetic number, because the mean of its divisors is an integer number (164735865).

Almost surely, 2^1216551401 is an apocalyptic number.

It is an amenable number.

1216551401 is a deficient number, since it is larger than the sum of its proper divisors (101335519).

1216551401 is an frugal number, since it uses more digits than its factorization.

1216551401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553772 (or 553746 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 26.

The square root of 1216551401 is about 34879.0969063134. The cubic root of 1216551401 is about 1067.5219683698.

The spelling of 1216551401 in words is "one billion, two hundred sixteen million, five hundred fifty-one thousand, four hundred one".