1221213516 has 48 divisors (see below), whose sum is σ = 2878363488. Its totient is φ = 402969600.

The previous prime is 1221213509. The next prime is 1221213529. The reversal of 1221213516 is 6153121221.

It is a happy number.

It is a super-2 number, since 2×1221213516² = 2982724903322164512, which contains 22 as substring.

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, 522286 + ... + 524618.

It is an arithmetic number, because the mean of its divisors is an integer number (59965906).

Almost surely, 2^1221213516 is an apocalyptic number.

It is an amenable number.

1221213516 is an abundant number, since it is smaller than the sum of its proper divisors (1657149972).

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

1221213516 is a wasteful number, since it uses less digits than its factorization.

1221213516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2762 (or 2760 counting only the distinct ones).

The product of its digits is 720, while the sum is 24.

The square root of 1221213516 is about 34945.8655065231. The cubic root of 1221213516 is about 1068.8838963327.

Adding to 1221213516 its reverse (6153121221), we get a palindrome (7374334737).

The spelling of 1221213516 in words is "one billion, two hundred twenty-one million, two hundred thirteen thousand, five hundred sixteen".