21147075 has 54 divisors (see below), whose sum is σ = 39956644. Its totient is φ = 11087280.

The previous prime is 21147073. The next prime is 21147079. The reversal of 21147075 is 57074112.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It is not a de Polignac number, because 21147075 - 2¹ = 21147073 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21147073) by changing a digit.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 358396 + ... + 358454.

Almost surely, 2^21147075 is an apocalyptic number.

21147075 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21147075 is a deficient number, since it is larger than the sum of its proper divisors (18809569).

21147075 is an frugal number, since it uses more digits than its factorization.

21147075 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143 (or 67 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21147075 is about 4598.5948940954. The cubic root of 21147075 is about 276.5349972651.

Multiplying 21147075 by its sum of digits (27), we get a square (570971025 = 23895²).

21147075 divided by its sum of digits (27) gives a square (783225 = 885²).

The spelling of 21147075 in words is "twenty-one million, one hundred forty-seven thousand, seventy-five".