133981621 has 4 divisors (see below), whose sum is σ = 134007244. Its totient is φ = 133956000.

The previous prime is 133981619. The next prime is 133981649. The reversal of 133981621 is 126189331.

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 579121 + 133402500 = 761^2 + 11550^2 .

It is a 3-Lehmer number, since φ(133981621) divides (133981621-1)³.

It is a cyclic number.

It is not a de Polignac number, because 133981621 - 2¹ = 133981619 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 (133981021) 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, 1830 + ... + 16471.

It is an arithmetic number, because the mean of its divisors is an integer number (33501811).

Almost surely, 2^133981621 is an apocalyptic number.

133981621 is the 7321-st heptagonal number.

It is an amenable number.

133981621 is a deficient number, since it is larger than the sum of its proper divisors (25623).

133981621 is an equidigital number, since it uses as much as digits as its factorization.

133981621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25622.

The product of its digits is 7776, while the sum is 34.

The square root of 133981621 is about 11575.0430236781. The cubic root of 133981621 is about 511.6995982063.

The spelling of 133981621 in words is "one hundred thirty-three million, nine hundred eighty-one thousand, six hundred twenty-one".