21954251 has 4 divisors (see below), whose sum is σ = 23950104. Its totient is φ = 19958400.

The previous prime is 21954241. The next prime is 21954263. The reversal of 21954251 is 15245912.

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

It is not a de Polignac number, because 21954251 - 2⁶ = 21954187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21954211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 997910 + ... + 997931.

It is an arithmetic number, because the mean of its divisors is an integer number (5987526).

Almost surely, 2^21954251 is an apocalyptic number.

21954251 is a deficient number, since it is larger than the sum of its proper divisors (1995853).

21954251 is a wasteful number, since it uses less digits than its factorization.

21954251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1995852.

The product of its digits is 3600, while the sum is 29.

The square root of 21954251 is about 4685.5363620401. The cubic root of 21954251 is about 280.0095702511.

It can be divided in two parts, 2195 and 4251, that added together give a palindrome (6446).

The spelling of 21954251 in words is "twenty-one million, nine hundred fifty-four thousand, two hundred fifty-one".