21438351 has 20 divisors (see below), whose sum is σ = 34938024. Its totient is φ = 12992400.

The previous prime is 21438349. The next prime is 21438353. The reversal of 21438351 is 15383412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21438349) and next prime (21438353).

It is not a de Polignac number, because 21438351 - 2¹ = 21438349 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438353) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 11140 + ... + 12921.

Almost surely, 2^21438351 is an apocalyptic number.

21438351 is a deficient number, since it is larger than the sum of its proper divisors (13499673).

21438351 is a wasteful number, since it uses less digits than its factorization.

21438351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24084 (or 24075 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21438351 is about 4630.1566928129. The cubic root of 21438351 is about 277.7988599051.

The spelling of 21438351 in words is "twenty-one million, four hundred thirty-eight thousand, three hundred fifty-one".