21645087 has 8 divisors (see below), whose sum is σ = 29291136. Its totient is φ = 14214552.

The previous prime is 21645079. The next prime is 21645101. The reversal of 21645087 is 78054612.

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

It is not a de Polignac number, because 21645087 - 2³ = 21645079 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645287) 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, 53643 + ... + 54044.

It is an arithmetic number, because the mean of its divisors is an integer number (3661392).

Almost surely, 2^21645087 is an apocalyptic number.

21645087 is a deficient number, since it is larger than the sum of its proper divisors (7646049).

21645087 is a wasteful number, since it uses less digits than its factorization.

21645087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107757.

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21645087 is about 4652.4280757471. The cubic root of 21645087 is about 278.6889687884.

Adding to 21645087 its reverse (78054612), we get a palindrome (99699699).

The spelling of 21645087 in words is "twenty-one million, six hundred forty-five thousand, eighty-seven".