21439887 has 16 divisors (see below), whose sum is σ = 34091520. Its totient is φ = 11718432.

The previous prime is 21439883. The next prime is 21439897. The reversal of 21439887 is 78893412.

It is not a de Polignac number, because 21439887 - 2² = 21439883 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21439883) 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 15 ways as a sum of consecutive naturals, for example, 21712 + ... + 22677.

It is an arithmetic number, because the mean of its divisors is an integer number (2130720).

Almost surely, 2^21439887 is an apocalyptic number.

21439887 is a deficient number, since it is larger than the sum of its proper divisors (12651633).

21439887 is a wasteful number, since it uses less digits than its factorization.

21439887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44422.

The product of its digits is 96768, while the sum is 42.

The square root of 21439887 is about 4630.3225589585. The cubic root of 21439887 is about 277.8054942596.

The spelling of 21439887 in words is "twenty-one million, four hundred thirty-nine thousand, eight hundred eighty-seven".