1220721656 has 32 divisors (see below), whose sum is σ = 2853636480. Its totient is φ = 475605600.

The previous prime is 1220721641. The next prime is 1220721661. The reversal of 1220721656 is 6561270221.

It is a super-2 number, since 2×1220721656² = 2980322722854764672, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 990230 + ... + 991461.

It is an arithmetic number, because the mean of its divisors is an integer number (89176140).

Almost surely, 2^1220721656 is an apocalyptic number.

It is an amenable number.

1220721656 is an abundant number, since it is smaller than the sum of its proper divisors (1632914824).

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

1220721656 is a wasteful number, since it uses less digits than its factorization.

1220721656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1981715 (or 1981711 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 1220721656 is about 34938.8273415122. The cubic root of 1220721656 is about 1068.7403746565.

Adding to 1220721656 its reverse (6561270221), we get a palindrome (7781991877).

The spelling of 1220721656 in words is "one billion, two hundred twenty million, seven hundred twenty-one thousand, six hundred fifty-six".