21478717 has 12 divisors (see below), whose sum is σ = 23590164. Its totient is φ = 19543680.

The previous prime is 21478679. The next prime is 21478729. The reversal of 21478717 is 71787412.

It can be written as a sum of positive squares in 6 ways, for example, as 9603801 + 11874916 = 3099^2 + 3446^2 .

It is not a de Polignac number, because 21478717 - 2²³ = 13090109 is a prime.

It is a super-2 number, since 2×21478717² = 922670567932178, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21478117) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11467 + ... + 13207.

It is an arithmetic number, because the mean of its divisors is an integer number (1965847).

Almost surely, 2^21478717 is an apocalyptic number.

It is an amenable number.

21478717 is a deficient number, since it is larger than the sum of its proper divisors (2111447).

21478717 is a wasteful number, since it uses less digits than its factorization.

21478717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1840 (or 1827 counting only the distinct ones).

The product of its digits is 21952, while the sum is 37.

The square root of 21478717 is about 4634.5136745941. The cubic root of 21478717 is about 277.9731052428.

The spelling of 21478717 in words is "twenty-one million, four hundred seventy-eight thousand, seven hundred seventeen".