21069581 has 8 divisors (see below), whose sum is σ = 22730904. Its totient is φ = 19414080.

The previous prime is 21069569. The next prime is 21069589. The reversal of 21069581 is 18596012.

It can be written as a sum of positive squares in 4 ways, for example, as 5593225 + 15476356 = 2365^2 + 3934^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21069581 is a prime.

It is a super-2 number, since 2×21069581² = 887854487031122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21069589) 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, 8771 + ... + 10911.

It is an arithmetic number, because the mean of its divisors is an integer number (2841363).

Almost surely, 2^21069581 is an apocalyptic number.

It is an amenable number.

21069581 is a deficient number, since it is larger than the sum of its proper divisors (1661323).

21069581 is a wasteful number, since it uses less digits than its factorization.

21069581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2911.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21069581 is about 4590.1613261409. The cubic root of 21069581 is about 276.1967939408.

The spelling of 21069581 in words is "twenty-one million, sixty-nine thousand, five hundred eighty-one".