21385825 has 12 divisors (see below), whose sum is σ = 26592048. Its totient is φ = 17061200.

The previous prime is 21385823. The next prime is 21385843. The reversal of 21385825 is 52858312.

It is not a de Polignac number, because 21385825 - 2¹ = 21385823 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21385823) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10110 + ... + 12040.

It is an arithmetic number, because the mean of its divisors is an integer number (2216004).

Almost surely, 2^21385825 is an apocalyptic number.

21385825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21385825 is a deficient number, since it is larger than the sum of its proper divisors (5206223).

21385825 is a wasteful number, since it uses less digits than its factorization.

21385825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2384 (or 2379 counting only the distinct ones).

The product of its digits is 19200, while the sum is 34.

The square root of 21385825 is about 4624.4810519668. The cubic root of 21385825 is about 277.5717964811.

It can be divided in two parts, 21 and 385825, that multiplied together give a triangular number (8102325 = T₄₀₂₅).

The spelling of 21385825 in words is "twenty-one million, three hundred eighty-five thousand, eight hundred twenty-five".