21387425 has 12 divisors (see below), whose sum is σ = 26605440. Its totient is φ = 17055120.

The previous prime is 21387419. The next prime is 21387437. The reversal of 21387425 is 52478312.

It is not a de Polignac number, because 21387425 - 2⁴ = 21387409 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21387391 and 21387400.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7784 + ... + 10166.

It is an arithmetic number, because the mean of its divisors is an integer number (2217120).

Almost surely, 2^21387425 is an apocalyptic number.

21387425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21387425 is a deficient number, since it is larger than the sum of its proper divisors (5218015).

21387425 is a wasteful number, since it uses less digits than its factorization.

21387425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2752 (or 2747 counting only the distinct ones).

The product of its digits is 13440, while the sum is 32.

The square root of 21387425 is about 4624.6540411149. The cubic root of 21387425 is about 277.5787185708.

It can be divided in two parts, 21387 and 425, that added together give a palindrome (21812).

The spelling of 21387425 in words is "twenty-one million, three hundred eighty-seven thousand, four hundred twenty-five".