137870021 has 4 divisors (see below), whose sum is σ = 138748332. Its totient is φ = 136991712.

The previous prime is 137870011. The next prime is 137870041. The reversal of 137870021 is 120078731.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120078731 = 613 ⋅195887.

It can be written as a sum of positive squares in 2 ways, for example, as 49773025 + 88096996 = 7055^2 + 9386^2 .

It is a cyclic number.

It is not a de Polignac number, because 137870021 - 2¹⁴ = 137853637 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (137870011) 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, 438920 + ... + 439233.

It is an arithmetic number, because the mean of its divisors is an integer number (34687083).

Almost surely, 2^137870021 is an apocalyptic number.

It is an amenable number.

137870021 is a deficient number, since it is larger than the sum of its proper divisors (878311).

137870021 is an equidigital number, since it uses as much as digits as its factorization.

137870021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 878310.

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 137870021 is about 11741.8065475463. The cubic root of 137870021 is about 516.6026313054.

The spelling of 137870021 in words is "one hundred thirty-seven million, eight hundred seventy thousand, twenty-one".