1220021989 has 2 divisors, whose sum is σ = 1220021990. Its totient is φ = 1220021988.

The previous prime is 1220021987. The next prime is 1220022029. The reversal of 1220021989 is 9891200221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 807525889 + 412496100 = 28417^2 + 20310^2 .

It is a cyclic number.

It is not a de Polignac number, because 1220021989 - 2¹ = 1220021987 is a prime.

It is a super-2 number, since 2×1220021989² = 2976907307287032242, which contains 22 as substring.

Together with 1220021987, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1220021987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610010994 + 610010995.

It is an arithmetic number, because the mean of its divisors is an integer number (610010995).

Almost surely, 2^1220021989 is an apocalyptic number.

It is an amenable number.

1220021989 is a deficient number, since it is larger than the sum of its proper divisors (1).

1220021989 is an equidigital number, since it uses as much as digits as its factorization.

1220021989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 1220021989 is about 34928.8131633470. The cubic root of 1220021989 is about 1068.5361497552.

The spelling of 1220021989 in words is "one billion, two hundred twenty million, twenty-one thousand, nine hundred eighty-nine".