21297478 has 4 divisors (see below), whose sum is σ = 31946220. Its totient is φ = 10648738.

The previous prime is 21297469. The next prime is 21297487. The reversal of 21297478 is 87479212.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21297469) and next prime (21297487).

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21297478.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5324368 + ... + 5324371.

It is an arithmetic number, because the mean of its divisors is an integer number (7986555).

Almost surely, 2^21297478 is an apocalyptic number.

21297478 is a deficient number, since it is larger than the sum of its proper divisors (10648742).

21297478 is a wasteful number, since it uses less digits than its factorization.

21297478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10648741.

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

The square root of 21297478 is about 4614.9190675460. The cubic root of 21297478 is about 277.1890432366.

The spelling of 21297478 in words is "twenty-one million, two hundred ninety-seven thousand, four hundred seventy-eight".