1220915981 has 2 divisors, whose sum is σ = 1220915982. Its totient is φ = 1220915980.

The previous prime is 1220915963. The next prime is 1220915989. The reversal of 1220915981 is 1895190221.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1178548900 + 42367081 = 34330^2 + 6509^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1220915981 is a prime.

It is a super-2 number, since 2×1220915981² = 2981271665322384722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1220915989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610457990 + 610457991.

It is an arithmetic number, because the mean of its divisors is an integer number (610457991).

Almost surely, 2^1220915981 is an apocalyptic number.

It is an amenable number.

1220915981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1220915981 is an equidigital number, since it uses as much as digits as its factorization.

1220915981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 38.

The square root of 1220915981 is about 34941.6081627621. The cubic root of 1220915981 is about 1068.7970820839.

The spelling of 1220915981 in words is "one billion, two hundred twenty million, nine hundred fifteen thousand, nine hundred eighty-one".