138787921 has 2 divisors, whose sum is σ = 138787922. Its totient is φ = 138787920.

The previous prime is 138787861. The next prime is 138787927. The reversal of 138787921 is 129787831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 136048896 + 2739025 = 11664^2 + 1655^2 .

It is a cyclic number.

It is not a de Polignac number, because 138787921 - 2¹⁵ = 138755153 is a prime.

It is not a weakly prime, because it can be changed into another prime (138787927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69393960 + 69393961.

It is an arithmetic number, because the mean of its divisors is an integer number (69393961).

Almost surely, 2^138787921 is an apocalyptic number.

It is an amenable number.

138787921 is a deficient number, since it is larger than the sum of its proper divisors (1).

138787921 is an equidigital number, since it uses as much as digits as its factorization.

138787921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 169344, while the sum is 46.

The square root of 138787921 is about 11780.8285362278. The cubic root of 138787921 is about 517.7465616211.

The spelling of 138787921 in words is "one hundred thirty-eight million, seven hundred eighty-seven thousand, nine hundred twenty-one".