21671439 has 8 divisors (see below), whose sum is σ = 29891760. Its totient is φ = 13949376.

The previous prime is 21671431. The next prime is 21671471. The reversal of 21671439 is 93417612.

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

It is not a de Polignac number, because 21671439 - 2³ = 21671431 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21671431) 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, 124462 + ... + 124635.

It is an arithmetic number, because the mean of its divisors is an integer number (3736470).

Almost surely, 2^21671439 is an apocalyptic number.

21671439 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21671439 is a deficient number, since it is larger than the sum of its proper divisors (8220321).

21671439 is a wasteful number, since it uses less digits than its factorization.

21671439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 249129.

The product of its digits is 9072, while the sum is 33.

The square root of 21671439 is about 4655.2592838638. The cubic root of 21671439 is about 278.8020203610.

The spelling of 21671439 in words is "twenty-one million, six hundred seventy-one thousand, four hundred thirty-nine".