1221312978 has 20 divisors (see below), whose sum is σ = 2736646110. Its totient is φ = 407104272.

The previous prime is 1221312977. The next prime is 1221313007. The reversal of 1221312978 is 8792131221.

It can be written as a sum of positive squares in only one way, i.e., 996222969 + 225090009 = 31563^2 + 15003^2 .

It is not an unprimeable number, because it can be changed into a prime (1221312977) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 3769323 + ... + 3769646.

Almost surely, 2^1221312978 is an apocalyptic number.

1221312978 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1221312978 is an abundant number, since it is smaller than the sum of its proper divisors (1515333132).

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

1221312978 is an equidigital number, since it uses as much as digits as its factorization.

1221312978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7538983 (or 7538974 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 1221312978 is about 34947.2885643507. The cubic root of 1221312978 is about 1068.9129140386.

The spelling of 1221312978 in words is "one billion, two hundred twenty-one million, three hundred twelve thousand, nine hundred seventy-eight".