21381529 has 8 divisors (see below), whose sum is σ = 24381000. Its totient is φ = 18575616.

The previous prime is 21381527. The next prime is 21381539. The reversal of 21381529 is 92518312.

It can be written as a sum of positive squares in 4 ways, for example, as 6350400 + 15031129 = 2520^2 + 3877^2 .

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 21381529 - 2¹ = 21381527 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 21381529.

It is not an unprimeable number, because it can be changed into a prime (21381527) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48154 + ... + 48595.

It is an arithmetic number, because the mean of its divisors is an integer number (3047625).

Almost surely, 2^21381529 is an apocalyptic number.

It is an amenable number.

21381529 is a deficient number, since it is larger than the sum of its proper divisors (2999471).

21381529 is a wasteful number, since it uses less digits than its factorization.

21381529 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96779.

The product of its digits is 4320, while the sum is 31.

The square root of 21381529 is about 4624.0165440881. The cubic root of 21381529 is about 277.5532089620.

The spelling of 21381529 in words is "twenty-one million, three hundred eighty-one thousand, five hundred twenty-nine".