21887521 has 4 divisors (see below), whose sum is σ = 22018752. Its totient is φ = 21756292.

The previous prime is 21887507. The next prime is 21887533. The reversal of 21887521 is 12578812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21887521 - 2¹³ = 21879329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21887821) 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 3 ways as a sum of consecutive naturals, for example, 65365 + ... + 65698.

It is an arithmetic number, because the mean of its divisors is an integer number (5504688).

Almost surely, 2^21887521 is an apocalyptic number.

It is an amenable number.

21887521 is a deficient number, since it is larger than the sum of its proper divisors (131231).

21887521 is a wasteful number, since it uses less digits than its factorization.

21887521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131230.

The product of its digits is 8960, while the sum is 34.

The square root of 21887521 is about 4678.4100931834. The cubic root of 21887521 is about 279.7255857397.

The spelling of 21887521 in words is "twenty-one million, eight hundred eighty-seven thousand, five hundred twenty-one".