21413987 has 4 divisors (see below), whose sum is σ = 24473136. Its totient is φ = 18354840.

The previous prime is 21413971. The next prime is 21413993. The reversal of 21413987 is 78931412.

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

It is not a de Polignac number, because 21413987 - 2⁴ = 21413971 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21413947) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1529564 + ... + 1529577.

It is an arithmetic number, because the mean of its divisors is an integer number (6118284).

Almost surely, 2^21413987 is an apocalyptic number.

21413987 is a deficient number, since it is larger than the sum of its proper divisors (3059149).

21413987 is an equidigital number, since it uses as much as digits as its factorization.

21413987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3059148.

The product of its digits is 12096, while the sum is 35.

The square root of 21413987 is about 4627.5249324018. The cubic root of 21413987 is about 277.6935835085.

The spelling of 21413987 in words is "twenty-one million, four hundred thirteen thousand, nine hundred eighty-seven".