20387993 has 2 divisors, whose sum is σ = 20387994. Its totient is φ = 20387992.

The previous prime is 20387953. The next prime is 20388013. The reversal of 20387993 is 39978302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12475024 + 7912969 = 3532^2 + 2813^2 .

It is a cyclic number.

It is not a de Polignac number, because 20387993 - 2¹⁰ = 20386969 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20387993.

It is not a weakly prime, because it can be changed into another prime (20387953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10193996 + 10193997.

It is an arithmetic number, because the mean of its divisors is an integer number (10193997).

Almost surely, 2^20387993 is an apocalyptic number.

It is an amenable number.

20387993 is a deficient number, since it is larger than the sum of its proper divisors (1).

20387993 is an equidigital number, since it uses as much as digits as its factorization.

20387993 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81648, while the sum is 41.

The square root of 20387993 is about 4515.3065233714. The cubic root of 20387993 is about 273.1858234746.

The spelling of 20387993 in words is "twenty million, three hundred eighty-seven thousand, nine hundred ninety-three".