21504087 has 24 divisors (see below), whose sum is σ = 34049808. Its totient is φ = 12969600.

The previous prime is 21504083. The next prime is 21504097. The reversal of 21504087 is 78040512.

It is not a de Polignac number, because 21504087 - 2² = 21504083 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21504087.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21504083) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27433 + ... + 28205.

It is an arithmetic number, because the mean of its divisors is an integer number (1418742).

Almost surely, 2^21504087 is an apocalyptic number.

21504087 is the 2319-th decagonal number.

21504087 is a deficient number, since it is larger than the sum of its proper divisors (12545721).

21504087 is a wasteful number, since it uses less digits than its factorization.

21504087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1071 (or 1068 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21504087 is about 4637.2499393498. The cubic root of 21504087 is about 278.0825066082.

Adding to 21504087 its reverse (78040512), we get a palindrome (99544599).

The spelling of 21504087 in words is "twenty-one million, five hundred four thousand, eighty-seven".