21651371 has 8 divisors (see below), whose sum is σ = 25597920. Its totient is φ = 17918208.

The previous prime is 21651367. The next prime is 21651389. The reversal of 21651371 is 17315612.

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

It is not a de Polignac number, because 21651371 - 2² = 21651367 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21651371.

It is not an unprimeable number, because it can be changed into a prime (21651391) 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, 53126 + ... + 53531.

It is an arithmetic number, because the mean of its divisors is an integer number (3199740).

Almost surely, 2^21651371 is an apocalyptic number.

21651371 is a deficient number, since it is larger than the sum of its proper divisors (3946549).

21651371 is a wasteful number, since it uses less digits than its factorization.

21651371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106693.

The product of its digits is 1260, while the sum is 26.

The square root of 21651371 is about 4653.1033730189. The cubic root of 21651371 is about 278.7159358322.

Adding to 21651371 its reverse (17315612), we get a palindrome (38966983).

It can be divided in two parts, 21651 and 371, that added together give a palindrome (22022).

The spelling of 21651371 in words is "twenty-one million, six hundred fifty-one thousand, three hundred seventy-one".