20239981 has 2 divisors, whose sum is σ = 20239982. Its totient is φ = 20239980.

The previous prime is 20239951. The next prime is 20239987. The reversal of 20239981 is 18993202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19980900 + 259081 = 4470^2 + 509^2 .

It is a cyclic number.

It is not a de Polignac number, because 20239981 - 2⁵ = 20239949 is a prime.

It is a super-2 number, since 2×20239981² = 819313661760722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20239987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10119990 + 10119991.

It is an arithmetic number, because the mean of its divisors is an integer number (10119991).

Almost surely, 2^20239981 is an apocalyptic number.

It is an amenable number.

20239981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20239981 is an equidigital number, since it uses as much as digits as its factorization.

20239981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7776, while the sum is 34.

The square root of 20239981 is about 4498.8866400477. The cubic root of 20239981 is about 272.5231290864.

The spelling of 20239981 in words is "twenty million, two hundred thirty-nine thousand, nine hundred eighty-one".