21387351 has 4 divisors (see below), whose sum is σ = 28516472. Its totient is φ = 14258232.

The previous prime is 21387347. The next prime is 21387361. The reversal of 21387351 is 15378312.

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

It is not a de Polignac number, because 21387351 - 2² = 21387347 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387341) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3564556 + ... + 3564561.

It is an arithmetic number, because the mean of its divisors is an integer number (7129118).

Almost surely, 2^21387351 is an apocalyptic number.

21387351 is a deficient number, since it is larger than the sum of its proper divisors (7129121).

21387351 is an equidigital number, since it uses as much as digits as its factorization.

21387351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7129120.

The product of its digits is 5040, while the sum is 30.

The square root of 21387351 is about 4624.6460405095. The cubic root of 21387351 is about 277.5783984318.

The spelling of 21387351 in words is "twenty-one million, three hundred eighty-seven thousand, three hundred fifty-one".