21378533 has 8 divisors (see below), whose sum is σ = 23472480. Its totient is φ = 19309680.

The previous prime is 21378529. The next prime is 21378541. The reversal of 21378533 is 33587312.

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

It is a cyclic number.

It is not a de Polignac number, because 21378533 - 2² = 21378529 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21378533.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378593) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4463 + ... + 7916.

It is an arithmetic number, because the mean of its divisors is an integer number (2934060).

Almost surely, 2^21378533 is an apocalyptic number.

It is an amenable number.

21378533 is a deficient number, since it is larger than the sum of its proper divisors (2093947).

21378533 is a wasteful number, since it uses less digits than its factorization.

21378533 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12547.

The product of its digits is 15120, while the sum is 32.

The square root of 21378533 is about 4623.6925719602. The cubic root of 21378533 is about 277.5402446840.

The spelling of 21378533 in words is "twenty-one million, three hundred seventy-eight thousand, five hundred thirty-three".