21006425 has 12 divisors (see below), whose sum is σ = 28416336. Its totient is φ = 15277200.

The previous prime is 21006421. The next prime is 21006431. The reversal of 21006425 is 52460012.

It is a happy number.

It is not a de Polignac number, because 21006425 - 2² = 21006421 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21006397 and 21006406.

It is not an unprimeable number, because it can be changed into a prime (21006421) 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, 37919 + ... + 38468.

It is an arithmetic number, because the mean of its divisors is an integer number (2368028).

Almost surely, 2^21006425 is an apocalyptic number.

21006425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21006425 is a deficient number, since it is larger than the sum of its proper divisors (7409911).

21006425 is a wasteful number, since it uses less digits than its factorization.

21006425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76408 (or 76403 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21006425 is about 4583.2766663164. The cubic root of 21006425 is about 275.9205514165.

Adding to 21006425 its reverse (52460012), we get a palindrome (73466437).

The spelling of 21006425 in words is "twenty-one million, six thousand, four hundred twenty-five".