21516425 has 24 divisors (see below), whose sum is σ = 31325376. Its totient is φ = 14351040.

The previous prime is 21516421. The next prime is 21516427. The reversal of 21516425 is 52461512.

It is not a de Polignac number, because 21516425 - 2² = 21516421 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is a junction number, because it is equal to n+sod(n) for n = 21516394 and 21516403.

It is not an unprimeable number, because it can be changed into a prime (21516421) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4814 + ... + 8136.

It is an arithmetic number, because the mean of its divisors is an integer number (1305224).

Almost surely, 2^21516425 is an apocalyptic number.

21516425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21516425 is a deficient number, since it is larger than the sum of its proper divisors (9808951).

21516425 is a wasteful number, since it uses less digits than its factorization.

21516425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3377 (or 3372 counting only the distinct ones).

The product of its digits is 2400, while the sum is 26.

The square root of 21516425 is about 4638.5800629072. The cubic root of 21516425 is about 278.1356798491.

Adding to 21516425 its reverse (52461512), we get a palindrome (73977937).

The spelling of 21516425 in words is "twenty-one million, five hundred sixteen thousand, four hundred twenty-five".