139997521 has 4 divisors (see below), whose sum is σ = 140347044. Its totient is φ = 139648000.

The previous prime is 139997489. The next prime is 139997531. The reversal of 139997521 is 125799931.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 129140496 + 10857025 = 11364^2 + 3295^2 .

It is a cyclic number.

It is not a de Polignac number, because 139997521 - 2⁵ = 139997489 is a prime.

It is a super-2 number, since 2×139997521² = 39198611772290882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (139997531) 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, 174160 + ... + 174961.

It is an arithmetic number, because the mean of its divisors is an integer number (35086761).

Almost surely, 2^139997521 is an apocalyptic number.

It is an amenable number.

139997521 is a deficient number, since it is larger than the sum of its proper divisors (349523).

139997521 is an equidigital number, since it uses as much as digits as its factorization.

139997521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 349522.

The product of its digits is 153090, while the sum is 46.

The square root of 139997521 is about 11832.0548088656. The cubic root of 139997521 is about 519.2463453592.

The spelling of 139997521 in words is "one hundred thirty-nine million, nine hundred ninety-seven thousand, five hundred twenty-one".