137689781 has 4 divisors (see below), whose sum is σ = 138953100. Its totient is φ = 136426464.

The previous prime is 137689771. The next prime is 137689787. The reversal of 137689781 is 187986731.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 187986731 = 17 ⋅11058043.

It can be written as a sum of positive squares in 2 ways, for example, as 95374756 + 42315025 = 9766^2 + 6505^2 .

It is a cyclic number.

It is not a de Polignac number, because 137689781 - 2¹⁴ = 137673397 is a prime.

It is a super-2 number, since 2×137689781² = 37916951583655922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (137689787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 631496 + ... + 631713.

It is an arithmetic number, because the mean of its divisors is an integer number (34738275).

Almost surely, 2^137689781 is an apocalyptic number.

It is an amenable number.

137689781 is a deficient number, since it is larger than the sum of its proper divisors (1263319).

137689781 is a wasteful number, since it uses less digits than its factorization.

137689781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1263318.

The product of its digits is 508032, while the sum is 50.

The square root of 137689781 is about 11734.1288982182. The cubic root of 137689781 is about 516.3774117762.

The spelling of 137689781 in words is "one hundred thirty-seven million, six hundred eighty-nine thousand, seven hundred eighty-one".