138749921 has 2 divisors, whose sum is σ = 138749922. Its totient is φ = 138749920.

The previous prime is 138749909. The next prime is 138749953. The reversal of 138749921 is 129947831.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80013025 + 58736896 = 8945^2 + 7664^2 .

It is a cyclic number.

It is not a de Polignac number, because 138749921 - 2¹⁸ = 138487777 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (138749621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69374960 + 69374961.

It is an arithmetic number, because the mean of its divisors is an integer number (69374961).

Almost surely, 2^138749921 is an apocalyptic number.

It is an amenable number.

138749921 is a deficient number, since it is larger than the sum of its proper divisors (1).

138749921 is an equidigital number, since it uses as much as digits as its factorization.

138749921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108864, while the sum is 44.

The square root of 138749921 is about 11779.2156360260. The cubic root of 138749921 is about 517.6993044701.

The spelling of 138749921 in words is "one hundred thirty-eight million, seven hundred forty-nine thousand, nine hundred twenty-one".