136981 has 8 divisors (see below), whose sum is σ = 151704. Its totient is φ = 122880.

The previous prime is 136979. The next prime is 136987. The reversal of 136981 is 189631.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8100 + 128881 = 90^2 + 359^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 7-Lehmer number, since φ(136981) divides (136981-1)⁷.

It is a cyclic number.

It is not a de Polignac number, because 136981 - 2¹ = 136979 is a prime.

It is a super-2 number, since 2×136981² = 37527588722, 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 (136987) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 405 + ... + 661.

It is an arithmetic number, because the mean of its divisors is an integer number (18963).

2¹³⁶⁹⁸¹ is an apocalyptic number.

It is an amenable number.

136981 is a deficient number, since it is larger than the sum of its proper divisors (14723).

136981 is a wasteful number, since it uses less digits than its factorization.

136981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311.

The product of its digits is 1296, while the sum is 28.

The square root of 136981 is about 370.1094432732. The cubic root of 136981 is about 51.5489840913.

Subtracting 136981 from its reverse (189631), we obtain a triangular number (52650 = T₃₂₄).

It can be divided in two parts, 1369 and 81, that multiplied together give a square (110889 = 333²).

The spelling of 136981 in words is "one hundred thirty-six thousand, nine hundred eighty-one".