1221657840 has 240 divisors, whose sum is σ = 4513961088. Its totient is φ = 294211584.

The previous prime is 1221657761. The next prime is 1221657869. The reversal of 1221657840 is 487561221.

It is a tau number, because it is divible by the number of its divisors (240).

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

It is a junction number, because it is equal to n+sod(n) for n = 1221657795 and 1221657804.

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 438532 + ... + 441308.

Almost surely, 2^1221657840 is an apocalyptic number.

1221657840 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 1221657840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2256980544).

1221657840 is an abundant number, since it is smaller than the sum of its proper divisors (3292303248).

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

1221657840 is a wasteful number, since it uses less digits than its factorization.

1221657840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2856 (or 2847 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 1221657840 is about 34952.2222469473. Note that the first 4 decimals coincide. The cubic root of 1221657840 is about 1069.0135141744.

The spelling of 1221657840 in words is "one billion, two hundred twenty-one million, six hundred fifty-seven thousand, eight hundred forty".