1221906720 has 96 divisors (see below), whose sum is σ = 4051615680. Its totient is φ = 308689920.

The previous prime is 1221906683. The next prime is 1221906727. The reversal of 1221906720 is 276091221.

It is a tau number, because it is divible by the number of its divisors (96).

It is a super-3 number, since 3×1221906720³ (a number of 28 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (1221906727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 57871 + ... + 76110.

It is an arithmetic number, because the mean of its divisors is an integer number (42204330).

Almost surely, 2^1221906720 is an apocalyptic number.

1221906720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221906720 is an abundant number, since it is smaller than the sum of its proper divisors (2829708960).

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

1221906720 is a wasteful number, since it uses less digits than its factorization.

1221906720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134018 (or 134010 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 1221906720 is about 34955.7823542830. The cubic root of 1221906720 is about 1069.0861035169.

Adding to 1221906720 its reverse (276091221), we get a palindrome (1497997941).

The spelling of 1221906720 in words is "one billion, two hundred twenty-one million, nine hundred six thousand, seven hundred twenty".