21147985 has 16 divisors (see below), whose sum is σ = 25945920. Its totient is φ = 16544320.

The previous prime is 21147967. The next prime is 21148013. The reversal of 21147985 is 58974112.

It is not a de Polignac number, because 21147985 - 2¹³ = 21139793 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54171 + ... + 54559.

It is an arithmetic number, because the mean of its divisors is an integer number (1621620).

Almost surely, 2^21147985 is an apocalyptic number.

It is an amenable number.

21147985 is a deficient number, since it is larger than the sum of its proper divisors (4797935).

21147985 is a wasteful number, since it uses less digits than its factorization.

21147985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 608.

The product of its digits is 20160, while the sum is 37.

The square root of 21147985 is about 4598.6938362974. The cubic root of 21147985 is about 276.5389638221.

The spelling of 21147985 in words is "twenty-one million, one hundred forty-seven thousand, nine hundred eighty-five".