1220721840 has 400 divisors, whose sum is σ = 4685929248. Its totient is φ = 292626432.

The previous prime is 1220721829. The next prime is 1220721851. The reversal of 1220721840 is 481270221.

1220721840 = 2275² + 2276² + ... + 2489².

It is an interprime number because it is at equal distance from previous prime (1220721829) and next prime (1220721851).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 3622152 + ... + 3622488.

Almost surely, 2^1220721840 is an apocalyptic number.

1220721840 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 1220721840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2342964624).

1220721840 is an abundant number, since it is smaller than the sum of its proper divisors (3465207408).

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

1220721840 is a wasteful number, since it uses less digits than its factorization.

1220721840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 418 (or 403 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 27.

The square root of 1220721840 is about 34938.8299746858. The cubic root of 1220721840 is about 1068.7404283538.

The spelling of 1220721840 in words is "one billion, two hundred twenty million, seven hundred twenty-one thousand, eight hundred forty".