21447447 has 32 divisors (see below), whose sum is σ = 35136000. Its totient is φ = 11600064.

The previous prime is 21447427. The next prime is 21447509. The reversal of 21447447 is 74474412.

It is a happy number.

It is not a de Polignac number, because 21447447 - 2¹⁴ = 21431063 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21447407) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19003 + ... + 20099.

It is an arithmetic number, because the mean of its divisors is an integer number (1098000).

Almost surely, 2^21447447 is an apocalyptic number.

21447447 is a deficient number, since it is larger than the sum of its proper divisors (13688553).

21447447 is a wasteful number, since it uses less digits than its factorization.

21447447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1140 (or 1126 counting only the distinct ones).

The product of its digits is 25088, while the sum is 33.

The square root of 21447447 is about 4631.1388448199. The cubic root of 21447447 is about 277.8381431059.

It can be divided in two parts, 2144 and 7447, that added together give a triangular number (9591 = T₁₃₈).

The spelling of 21447447 in words is "twenty-one million, four hundred forty-seven thousand, four hundred forty-seven".