21154191 has 4 divisors (see below), whose sum is σ = 28205592. Its totient is φ = 14102792.

The previous prime is 21154187. The next prime is 21154193. The reversal of 21154191 is 19145112.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21154191 - 2² = 21154187 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21154193) 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, 3525696 + ... + 3525701.

It is an arithmetic number, because the mean of its divisors is an integer number (7051398).

Almost surely, 2^21154191 is an apocalyptic number.

21154191 is a deficient number, since it is larger than the sum of its proper divisors (7051401).

21154191 is an equidigital number, since it uses as much as digits as its factorization.

21154191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7051400.

The product of its digits is 360, while the sum is 24.

The square root of 21154191 is about 4599.3685436155. The cubic root of 21154191 is about 276.5660118358.

The spelling of 21154191 in words is "twenty-one million, one hundred fifty-four thousand, one hundred ninety-one".