20121989 has 2 divisors, whose sum is σ = 20121990. Its totient is φ = 20121988.

The previous prime is 20121973. The next prime is 20122031. The reversal of 20121989 is 98912102.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19731364 + 390625 = 4442^2 + 625^2 .

It is a cyclic number.

It is not a de Polignac number, because 20121989 - 2⁴ = 20121973 is a prime.

It is a super-2 number, since 2×20121989² = 809788882632242, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20121919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10060994 + 10060995.

It is an arithmetic number, because the mean of its divisors is an integer number (10060995).

Almost surely, 2^20121989 is an apocalyptic number.

It is an amenable number.

20121989 is a deficient number, since it is larger than the sum of its proper divisors (1).

20121989 is an equidigital number, since it uses as much as digits as its factorization.

20121989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 20121989 is about 4485.7540057386. The cubic root of 20121989 is about 271.9925252055.

The spelling of 20121989 in words is "twenty million, one hundred twenty-one thousand, nine hundred eighty-nine".