21287479 has 8 divisors (see below), whose sum is σ = 22084560. Its totient is φ = 20494656.

The previous prime is 21287459. The next prime is 21287531. The reversal of 21287479 is 97478212.

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

It is a cyclic number.

It is not a de Polignac number, because 21287479 - 2⁵ = 21287447 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287449) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12019 + ... + 13675.

It is an arithmetic number, because the mean of its divisors is an integer number (2760570).

Almost surely, 2^21287479 is an apocalyptic number.

21287479 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21287479 is a deficient number, since it is larger than the sum of its proper divisors (797081).

21287479 is a wasteful number, since it uses less digits than its factorization.

21287479 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2129.

The product of its digits is 56448, while the sum is 40.

The square root of 21287479 is about 4613.8356060874. The cubic root of 21287479 is about 277.1456570807.

The spelling of 21287479 in words is "twenty-one million, two hundred eighty-seven thousand, four hundred seventy-nine".