21384985 has 16 divisors (see below), whose sum is σ = 26666640. Its totient is φ = 16450560.

The previous prime is 21384983. The next prime is 21384991. The reversal of 21384985 is 58948312.

It can be written as a sum of positive squares in 8 ways, for example, as 6431296 + 14953689 = 2536^2 + 3867^2 .

It is not a de Polignac number, because 21384985 - 2¹ = 21384983 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21384983) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14251 + ... + 15679.

It is an arithmetic number, because the mean of its divisors is an integer number (1666665).

Almost surely, 2^21384985 is an apocalyptic number.

It is an amenable number.

21384985 is a deficient number, since it is larger than the sum of its proper divisors (5281655).

21384985 is a wasteful number, since it uses less digits than its factorization.

21384985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1548.

The product of its digits is 69120, while the sum is 40.

The square root of 21384985 is about 4624.3902300736. The cubic root of 21384985 is about 277.5681622458.

The spelling of 21384985 in words is "twenty-one million, three hundred eighty-four thousand, nine hundred eighty-five".