21523087 has 4 divisors (see below), whose sum is σ = 21665776. Its totient is φ = 21380400.

The previous prime is 21523069. The next prime is 21523093. The reversal of 21523087 is 78032512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21523087 - 2¹⁵ = 21490319 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 9.

It is a zygodrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523387) 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, 71118 + ... + 71419.

It is an arithmetic number, because the mean of its divisors is an integer number (5416444).

Almost surely, 2^21523087 is an apocalyptic number.

21523087 is the 2679-th hex number.

21523087 is a deficient number, since it is larger than the sum of its proper divisors (142689).

21523087 is a wasteful number, since it uses less digits than its factorization.

21523087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142688.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 21523087 is about 4639.2981150170. The cubic root of 21523087 is about 278.1643827074.

Adding to 21523087 its reverse (78032512), we get a palindrome (99555599).

The spelling of 21523087 in words is "twenty-one million, five hundred twenty-three thousand, eighty-seven".