1221534720 has 396 divisors, whose sum is σ = 4932721404. Its totient is φ = 278691840.

The previous prime is 1221534709. The next prime is 1221534737. The reversal of 1221534720 is 274351221.

1221534720 is a `hidden beast` number, since 122 + 1 + 534 + 7 + 2 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 462422016 + 759112704 = 21504^2 + 27552^2 .

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 2257650 + ... + 2258190.

Almost surely, 2^1221534720 is an apocalyptic number.

1221534720 is a gapful number since it is divisible by the number (10) 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 1221534720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2466360702).

1221534720 is an abundant number, since it is smaller than the sum of its proper divisors (3711186684).

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

1221534720 is a wasteful number, since it uses less digits than its factorization.

1221534720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 586 (or 558 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 1221534720 is about 34950.4609411664. The cubic root of 1221534720 is about 1068.9776008547.

Adding to 1221534720 its reverse (274351221), we get a palindrome (1495885941).

The spelling of 1221534720 in words is "one billion, two hundred twenty-one million, five hundred thirty-four thousand, seven hundred twenty".