21375647 has 16 divisors (see below), whose sum is σ = 23887872. Its totient is φ = 19032960.

The previous prime is 21375631. The next prime is 21375659. The reversal of 21375647 is 74657312.

It is a cyclic number.

It is not a de Polignac number, because 21375647 - 2⁴ = 21375631 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 (21375617) 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 15 ways as a sum of consecutive naturals, for example, 24338 + ... + 25200.

It is an arithmetic number, because the mean of its divisors is an integer number (1492992).

Almost surely, 2^21375647 is an apocalyptic number.

21375647 is a deficient number, since it is larger than the sum of its proper divisors (2512225).

21375647 is a wasteful number, since it uses less digits than its factorization.

21375647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 958.

The product of its digits is 35280, while the sum is 35.

The square root of 21375647 is about 4623.3804732036. The cubic root of 21375647 is about 277.5277552522.

It can be divided in two parts, 21375 and 647, that added together give a palindrome (22022).

The spelling of 21375647 in words is "twenty-one million, three hundred seventy-five thousand, six hundred forty-seven".