21351672 has 24 divisors (see below), whose sum is σ = 57827640. Its totient is φ = 7117200.

The previous prime is 21351661. The next prime is 21351679. The reversal of 21351672 is 27615312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21351679) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 148204 + ... + 148347.

It is an arithmetic number, because the mean of its divisors is an integer number (2409485).

Almost surely, 2^21351672 is an apocalyptic number.

It is an amenable number.

21351672 is an abundant number, since it is smaller than the sum of its proper divisors (36475968).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21351672 is a wasteful number, since it uses less digits than its factorization.

21351672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296563 (or 296556 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21351672 is about 4620.7869459649. The cubic root of 21351672 is about 277.4239577375.

Adding to 21351672 its reverse (27615312), we get a palindrome (48966984).

The spelling of 21351672 in words is "twenty-one million, three hundred fifty-one thousand, six hundred seventy-two".