21006427 has 8 divisors (see below), whose sum is σ = 22720320. Its totient is φ = 19306560.

The previous prime is 21006421. The next prime is 21006431. The reversal of 21006427 is 72460012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21006427 - 2²³ = 12617819 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21006398 and 21006407.

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 7 ways as a sum of consecutive naturals, for example, 274 + ... + 6487.

It is an arithmetic number, because the mean of its divisors is an integer number (2840040).

Almost surely, 2^21006427 is an apocalyptic number.

21006427 is a deficient number, since it is larger than the sum of its proper divisors (1713893).

21006427 is a wasteful number, since it uses less digits than its factorization.

21006427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7013.

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 21006427 is about 4583.2768845009. The cubic root of 21006427 is about 275.9205601732.

Adding to 21006427 its reverse (72460012), we get a palindrome (93466439).

The spelling of 21006427 in words is "twenty-one million, six thousand, four hundred twenty-seven".