21402087 has 32 divisors (see below), whose sum is σ = 34145280. Its totient is φ = 11665920.

The previous prime is 21402079. The next prime is 21402091. The reversal of 21402087 is 78020412.

It is not a de Polignac number, because 21402087 - 2³ = 21402079 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21402047) 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 31 ways as a sum of consecutive naturals, for example, 68662 + ... + 68972.

It is an arithmetic number, because the mean of its divisors is an integer number (1067040).

Almost surely, 2^21402087 is an apocalyptic number.

21402087 is a deficient number, since it is larger than the sum of its proper divisors (12743193).

21402087 is a wasteful number, since it uses less digits than its factorization.

21402087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 463.

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21402087 is about 4626.2389691844. The cubic root of 21402087 is about 277.6421347995.

Adding to 21402087 its reverse (78020412), we get a palindrome (99422499).

The spelling of 21402087 in words is "twenty-one million, four hundred two thousand, eighty-seven".