1221516156 has 96 divisors (see below), whose sum is σ = 3450101760. Its totient is φ = 328584384.

The previous prime is 1221516143. The next prime is 1221516169. The reversal of 1221516156 is 6516151221.

It is an interprime number because it is at equal distance from previous prime (1221516143) and next prime (1221516169).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 264241 + ... + 268823.

It is an arithmetic number, because the mean of its divisors is an integer number (35938560).

Almost surely, 2^1221516156 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221516156, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1725050880).

1221516156 is an abundant number, since it is smaller than the sum of its proper divisors (2228585604).

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

1221516156 is a wasteful number, since it uses less digits than its factorization.

1221516156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4783 (or 4781 counting only the distinct ones).

The product of its digits is 3600, while the sum is 30.

The square root of 1221516156 is about 34950.1953642608. The cubic root of 1221516156 is about 1068.9721856448.

Adding to 1221516156 its reverse (6516151221), we get a palindrome (7737667377).

The spelling of 1221516156 in words is "one billion, two hundred twenty-one million, five hundred sixteen thousand, one hundred fifty-six".