21453987 has 4 divisors (see below), whose sum is σ = 28605320. Its totient is φ = 14302656.

The previous prime is 21453979. The next prime is 21454007. The reversal of 21453987 is 78935412.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21453987 - 2³ = 21453979 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21453937) 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, 3575662 + ... + 3575667.

It is an arithmetic number, because the mean of its divisors is an integer number (7151330).

Almost surely, 2^21453987 is an apocalyptic number.

21453987 is a deficient number, since it is larger than the sum of its proper divisors (7151333).

21453987 is an equidigital number, since it uses as much as digits as its factorization.

21453987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7151332.

The product of its digits is 60480, while the sum is 39.

The square root of 21453987 is about 4631.8448808223. The cubic root of 21453987 is about 277.8663807604.

The spelling of 21453987 in words is "twenty-one million, four hundred fifty-three thousand, nine hundred eighty-seven".