138791961 has 135 divisors (see below), whose sum is σ = 281611407. Its totient is φ = 67858560.

The previous prime is 138791909. The next prime is 138791963. The reversal of 138791961 is 169197831.

138791961 = 214² + 215² + ... + 752².

138791961 = 1³ + 2³ + ... + 153³.

The square root of 138791961 is 11781.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 108056025 + 30735936 = 10395^2 + 5544^2 .

It is not a de Polignac number, because 138791961 - 2⁷ = 138791833 is a prime.

It is not an unprimeable number, because it can be changed into a prime (138791963) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 8164225 + ... + 8164241.

Almost surely, 2^138791961 is an apocalyptic number.

138791961 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

138791961 is the 11781-st square number.

138791961 is the 5891-st centered octagonal number.

It is an amenable number.

138791961 is an abundant number, since it is smaller than the sum of its proper divisors (142819446).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

138791961 is a wasteful number, since it uses less digits than its factorization.

138791961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82 (or 38 counting only the distinct ones).

The product of its digits is 81648, while the sum is 45.

The cubic root of 138791961 is about 517.7515852951.

The spelling of 138791961 in words is "one hundred thirty-eight million, seven hundred ninety-one thousand, nine hundred sixty-one".