21090087 has 6 divisors (see below), whose sum is σ = 30463472. Its totient is φ = 14060052.

The previous prime is 21090073. The next prime is 21090101. The reversal of 21090087 is 78009012.

It is an interprime number because it is at equal distance from previous prime (21090073) and next prime (21090101).

It is not a de Polignac number, because 21090087 - 2⁴ = 21090071 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 21090087.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090007) 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 5 ways as a sum of consecutive naturals, for example, 1171663 + ... + 1171680.

Almost surely, 2^21090087 is an apocalyptic number.

21090087 is a deficient number, since it is larger than the sum of its proper divisors (9373385).

21090087 is a wasteful number, since it uses less digits than its factorization.

21090087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2343349 (or 2343346 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 21090087 is about 4592.3944734746. The cubic root of 21090087 is about 276.2863678634.

Adding to 21090087 its reverse (78009012), we get a palindrome (99099099).

The spelling of 21090087 in words is "twenty-one million, ninety thousand, eighty-seven".