20139997 has 2 divisors, whose sum is σ = 20139998. Its totient is φ = 20139996.

The previous prime is 20139991. The next prime is 20140027. The reversal of 20139997 is 79993102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18567481 + 1572516 = 4309^2 + 1254^2 .

It is a cyclic number.

It is not a de Polignac number, because 20139997 - 2⁷ = 20139869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20139991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10069998 + 10069999.

It is an arithmetic number, because the mean of its divisors is an integer number (10069999).

Almost surely, 2^20139997 is an apocalyptic number.

It is an amenable number.

20139997 is a deficient number, since it is larger than the sum of its proper divisors (1).

20139997 is an equidigital number, since it uses as much as digits as its factorization.

20139997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30618, while the sum is 40.

The square root of 20139997 is about 4487.7608002210. The cubic root of 20139997 is about 272.0736401318.

The spelling of 20139997 in words is "twenty million, one hundred thirty-nine thousand, nine hundred ninety-seven".