21506427 has 24 divisors (see below), whose sum is σ = 32104800. Its totient is φ = 13864320.

The previous prime is 21506417. The next prime is 21506431. The reversal of 21506427 is 72460512.

21506427 is a `hidden beast` number, since 2 + 15 + 0 + 642 + 7 = 666.

It is not a de Polignac number, because 21506427 - 2¹⁴ = 21490043 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21506427.

It is not an unprimeable number, because it can be changed into a prime (21506417) 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, 61449 + ... + 61797.

It is an arithmetic number, because the mean of its divisors is an integer number (1337700).

Almost surely, 2^21506427 is an apocalyptic number.

21506427 is a deficient number, since it is larger than the sum of its proper divisors (10598373).

21506427 is a wasteful number, since it uses less digits than its factorization.

21506427 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 563 (or 560 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21506427 is about 4637.5022371962. The cubic root of 21506427 is about 278.0925928996.

Adding to 21506427 its reverse (72460512), we get a palindrome (93966939).

The spelling of 21506427 in words is "twenty-one million, five hundred six thousand, four hundred twenty-seven".