1221526656 has 160 divisors (see below), whose sum is σ = 4154810880. Its totient is φ = 348986880.

The previous prime is 1221526651. The next prime is 1221526667. The reversal of 1221526656 is 6566251221.

1221526656 is a `hidden beast` number, since 122 + 1 + 526 + 6 + 5 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 1221526656.

It is not an unprimeable number, because it can be changed into a prime (1221526651) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 64161 + ... + 80991.

It is an arithmetic number, because the mean of its divisors is an integer number (25967568).

Almost surely, 2^1221526656 is an apocalyptic number.

1221526656 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221526656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2077405440).

1221526656 is an abundant number, since it is smaller than the sum of its proper divisors (2933284224).

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

1221526656 is an equidigital number, since it uses as much as digits as its factorization.

1221526656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16864 (or 16843 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 1221526656 is about 34950.3455776906. The cubic root of 1221526656 is about 1068.9752485531.

Adding to 1221526656 its reverse (6566251221), we get a palindrome (7787777877).

The spelling of 1221526656 in words is "one billion, two hundred twenty-one million, five hundred twenty-six thousand, six hundred fifty-six".