21384481 has 4 divisors (see below), whose sum is σ = 22510000. Its totient is φ = 20258964.

The previous prime is 21384479. The next prime is 21384509. The reversal of 21384481 is 18448312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21384481 - 2¹ = 21384479 is a prime.

It is a super-2 number, since 2×21384481² = 914592055278722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21384421) 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, 562731 + ... + 562768.

It is an arithmetic number, because the mean of its divisors is an integer number (5627500).

Almost surely, 2^21384481 is an apocalyptic number.

It is an amenable number.

21384481 is a deficient number, since it is larger than the sum of its proper divisors (1125519).

21384481 is a wasteful number, since it uses less digits than its factorization.

21384481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1125518.

The product of its digits is 6144, while the sum is 31.

The square root of 21384481 is about 4624.3357360815. The cubic root of 21384481 is about 277.5659816589.

Adding to 21384481 its product of digits (6144), we get a square (21390625 = 4625²).

The spelling of 21384481 in words is "twenty-one million, three hundred eighty-four thousand, four hundred eighty-one".