21154251 has 8 divisors (see below), whose sum is σ = 28668304. Its totient is φ = 13871520.

The previous prime is 21154207. The next prime is 21154283. The reversal of 21154251 is 15245112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21154251 - 2⁶ = 21154187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21354251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57616 + ... + 57981.

It is an arithmetic number, because the mean of its divisors is an integer number (3583538).

Almost surely, 2^21154251 is an apocalyptic number.

21154251 is a deficient number, since it is larger than the sum of its proper divisors (7514053).

21154251 is a wasteful number, since it uses less digits than its factorization.

21154251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115661.

The product of its digits is 400, while the sum is 21.

The square root of 21154251 is about 4599.3750662454. The cubic root of 21154251 is about 276.5662733119.

Adding to 21154251 its reverse (15245112), we get a palindrome (36399363).

The spelling of 21154251 in words is "twenty-one million, one hundred fifty-four thousand, two hundred fifty-one".