21521087 has 8 divisors (see below), whose sum is σ = 25260576. Its totient is φ = 17947872.

The previous prime is 21521083. The next prime is 21521111. The reversal of 21521087 is 78012512.

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 21521087 - 2² = 21521083 is a prime.

It is a super-3 number, since 3×21521087³ (a number of 23 digits) contains 333 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 (21521083) 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, 41288 + ... + 41805.

It is an arithmetic number, because the mean of its divisors is an integer number (3157572).

Almost surely, 2^21521087 is an apocalyptic number.

21521087 is a deficient number, since it is larger than the sum of its proper divisors (3739489).

21521087 is an equidigital number, since it uses as much as digits as its factorization.

21521087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83137.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21521087 is about 4639.0825601621. The cubic root of 21521087 is about 278.1557664403.

Adding to 21521087 its reverse (78012512), we get a palindrome (99533599).

The spelling of 21521087 in words is "twenty-one million, five hundred twenty-one thousand, eighty-seven".