1216521005 has 16 divisors (see below), whose sum is σ = 1675305984. Its totient is φ = 830718720.

The previous prime is 1216520993. The next prime is 1216521013. The reversal of 1216521005 is 5001256121.

It is a happy number.

It is not a de Polignac number, because 1216521005 - 2¹⁰ = 1216519981 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 63677 + ... + 80546.

It is an arithmetic number, because the mean of its divisors is an integer number (104706624).

Almost surely, 2^1216521005 is an apocalyptic number.

It is an amenable number.

1216521005 is a deficient number, since it is larger than the sum of its proper divisors (458784979).

1216521005 is a wasteful number, since it uses less digits than its factorization.

1216521005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144476.

The product of its (nonzero) digits is 600, while the sum is 23.

The square root of 1216521005 is about 34878.6611698328. The cubic root of 1216521005 is about 1067.5130774815.

Adding to 1216521005 its reverse (5001256121), we get a palindrome (6217777126).

The spelling of 1216521005 in words is "one billion, two hundred sixteen million, five hundred twenty-one thousand, five".