21705425 has 24 divisors (see below), whose sum is σ = 31759872. Its totient is φ = 14400000.

The previous prime is 21705419. The next prime is 21705433. The reversal of 21705425 is 52450712.

It is not a de Polignac number, because 21705425 - 2¹⁶ = 21639889 is a prime.

It is a super-2 number, since 2×21705425² = 942250948861250, which contains 22 as substring.

It is a Smith number, since the sum of its digits (26) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21705394 and 21705403.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3425 + ... + 7425.

It is an arithmetic number, because the mean of its divisors is an integer number (1323328).

Almost surely, 2^21705425 is an apocalyptic number.

21705425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21705425 is a deficient number, since it is larger than the sum of its proper divisors (10054447).

21705425 is a wasteful number, since it uses less digits than its factorization.

21705425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4049 (or 4044 counting only the distinct ones).

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21705425 is about 4658.9081338872. The cubic root of 21705425 is about 278.9476869926.

The spelling of 21705425 in words is "twenty-one million, seven hundred five thousand, four hundred twenty-five".