20399947 has 2 divisors, whose sum is σ = 20399948. Its totient is φ = 20399946.

The previous prime is 20399921. The next prime is 20399969. The reversal of 20399947 is 74999302.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20399947 - 2¹⁹ = 19875659 is a prime.

It is not a weakly prime, because it can be changed into another prime (20399347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10199973 + 10199974.

It is an arithmetic number, because the mean of its divisors is an integer number (10199974).

Almost surely, 2^20399947 is an apocalyptic number.

20399947 is a deficient number, since it is larger than the sum of its proper divisors (1).

20399947 is an equidigital number, since it uses as much as digits as its factorization.

20399947 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 122472, while the sum is 43.

The square root of 20399947 is about 4516.6300490521. The cubic root of 20399947 is about 273.2392049803.

The spelling of 20399947 in words is "twenty million, three hundred ninety-nine thousand, nine hundred forty-seven".