21506847 has 4 divisors (see below), whose sum is σ = 28675800. Its totient is φ = 14337896.

The previous prime is 21506843. The next prime is 21506861. The reversal of 21506847 is 74860512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21506847 - 2² = 21506843 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506843) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3584472 + ... + 3584477.

It is an arithmetic number, because the mean of its divisors is an integer number (7168950).

Almost surely, 2^21506847 is an apocalyptic number.

21506847 is a deficient number, since it is larger than the sum of its proper divisors (7168953).

21506847 is an equidigital number, since it uses as much as digits as its factorization.

21506847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7168952.

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21506847 is about 4637.5475199722. The cubic root of 21506847 is about 278.0944031821.

The spelling of 21506847 in words is "twenty-one million, five hundred six thousand, eight hundred forty-seven".