139521681 has 24 divisors (see below), whose sum is σ = 218714496. Its totient is φ = 85194720.

The previous prime is 139521677. The next prime is 139521743. The reversal of 139521681 is 186125931.

It is not a de Polignac number, because 139521681 - 2² = 139521677 is a prime.

It is a super-2 number, since 2×139521681² = 38932598938131522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (139521631) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10776 + ... + 19878.

It is an arithmetic number, because the mean of its divisors is an integer number (9113104).

Almost surely, 2^139521681 is an apocalyptic number.

It is an amenable number.

139521681 is a deficient number, since it is larger than the sum of its proper divisors (79192815).

139521681 is a wasteful number, since it uses less digits than its factorization.

139521681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9253 (or 9250 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The square root of 139521681 is about 11811.9296052762. The cubic root of 139521681 is about 518.6573857791.

The spelling of 139521681 in words is "one hundred thirty-nine million, five hundred twenty-one thousand, six hundred eighty-one".