187121621 has 4 divisors (see below), whose sum is σ = 187468044. Its totient is φ = 186775200.

The previous prime is 187121603. The next prime is 187121639. The reversal of 187121621 is 126121781.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 126121781 = 41 ⋅3076141.

It is an interprime number because it is at equal distance from previous prime (187121603) and next prime (187121639).

It can be written as a sum of positive squares in 2 ways, for example, as 63600625 + 123520996 = 7975^2 + 11114^2 .

It is a cyclic number.

It is not a de Polignac number, because 187121621 - 2²⁶ = 120012757 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 (187123621) 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, 172400 + ... + 173481.

It is an arithmetic number, because the mean of its divisors is an integer number (46867011).

Almost surely, 2^187121621 is an apocalyptic number.

It is an amenable number.

187121621 is a deficient number, since it is larger than the sum of its proper divisors (346423).

187121621 is an equidigital number, since it uses as much as digits as its factorization.

187121621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 346422.

The product of its digits is 1344, while the sum is 29.

The square root of 187121621 is about 13679.2405125431. The cubic root of 187121621 is about 571.9718523730.

The spelling of 187121621 in words is "one hundred eighty-seven million, one hundred twenty-one thousand, six hundred twenty-one".