21264987 has 8 divisors (see below), whose sum is σ = 28517904. Its totient is φ = 14094368.

The previous prime is 21264979. The next prime is 21265001. The reversal of 21264987 is 78946212.

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

It is a cyclic number.

It is not a de Polignac number, because 21264987 - 2³ = 21264979 is a prime.

It is a super-2 number, since 2×21264987² = 904399344220338, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21264487) 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, 19968 + ... + 21005.

It is an arithmetic number, because the mean of its divisors is an integer number (3564738).

Almost surely, 2^21264987 is an apocalyptic number.

21264987 is a deficient number, since it is larger than the sum of its proper divisors (7252917).

21264987 is a wasteful number, since it uses less digits than its factorization.

21264987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41149.

The product of its digits is 48384, while the sum is 39.

The square root of 21264987 is about 4611.3975105167. The cubic root of 21264987 is about 277.0480135029.

The spelling of 21264987 in words is "twenty-one million, two hundred sixty-four thousand, nine hundred eighty-seven".