1221378667 has 2 divisors, whose sum is σ = 1221378668. Its totient is φ = 1221378666.

The previous prime is 1221378659. The next prime is 1221378673. The reversal of 1221378667 is 7668731221.

It is a strong prime.

It is an emirp because it is prime and its reverse (7668731221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221378667 - 2³ = 1221378659 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221388667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610689333 + 610689334.

It is an arithmetic number, because the mean of its divisors is an integer number (610689334).

Almost surely, 2^1221378667 is an apocalyptic number.

1221378667 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221378667 is an equidigital number, since it uses as much as digits as its factorization.

1221378667 is an evil number, because the sum of its binary digits is even.

The product of its digits is 169344, while the sum is 43.

The square root of 1221378667 is about 34948.2283814216. The cubic root of 1221378667 is about 1068.9320777208.

The spelling of 1221378667 in words is "one billion, two hundred twenty-one million, three hundred seventy-eight thousand, six hundred sixty-seven".