139902181 has 4 divisors (see below), whose sum is σ = 139928364. Its totient is φ = 139876000.

The previous prime is 139902173. The next prime is 139902193. The reversal of 139902181 is 181209931.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 181209931 = 7 ⋅25887133.

It can be written as a sum of positive squares in 2 ways, for example, as 73805281 + 66096900 = 8591^2 + 8130^2 .

It is a 3-Lehmer number, since φ(139902181) divides (139902181-1)³.

It is a cyclic number.

It is not a de Polignac number, because 139902181 - 2³ = 139902173 is a prime.

It is a super-2 number, since 2×139902181² = 39145240497113522, which contains 22 as substring.

It is a deceptive number, since it divides R_139902180.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (139902121) 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, 1870 + ... + 16831.

It is an arithmetic number, because the mean of its divisors is an integer number (34982091).

Almost surely, 2^139902181 is an apocalyptic number.

139902181 is the 7481-st heptagonal number.

It is an amenable number.

139902181 is a deficient number, since it is larger than the sum of its proper divisors (26183).

139902181 is an equidigital number, since it uses as much as digits as its factorization.

139902181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26182.

The product of its (nonzero) digits is 3888, while the sum is 34.

The square root of 139902181 is about 11828.0252366995. The cubic root of 139902181 is about 519.1284475843.

The spelling of 139902181 in words is "one hundred thirty-nine million, nine hundred two thousand, one hundred eighty-one".