21585145 has 16 divisors (see below), whose sum is σ = 26938368. Its totient is φ = 16585920.

The previous prime is 21585143. The next prime is 21585181. The reversal of 21585145 is 54158512.

21585145 = T₃₅ + T₃₆ + ... + T₅₀₅.

It is not a de Polignac number, because 21585145 - 2¹ = 21585143 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21585143) 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, 23892 + ... + 24778.

It is an arithmetic number, because the mean of its divisors is an integer number (1683648).

Almost surely, 2^21585145 is an apocalyptic number.

It is an amenable number.

21585145 is a deficient number, since it is larger than the sum of its proper divisors (5353223).

21585145 is a wasteful number, since it uses less digits than its factorization.

21585145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1080.

The product of its digits is 8000, while the sum is 31.

The square root of 21585145 is about 4645.9815970363. The cubic root of 21585145 is about 278.4314720402.

The spelling of 21585145 in words is "twenty-one million, five hundred eighty-five thousand, one hundred forty-five".