21378474 has 48 divisors (see below), whose sum is σ = 50424192. Its totient is φ = 6506784.

The previous prime is 21378457. The next prime is 21378491. The reversal of 21378474 is 47487312.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21378457) and next prime (21378491).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 23659 + ... + 24545.

It is an arithmetic number, because the mean of its divisors is an integer number (1050504).

Almost surely, 2^21378474 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21378474, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25212096).

21378474 is an abundant number, since it is smaller than the sum of its proper divisors (29045718).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21378474 is a wasteful number, since it uses less digits than its factorization.

21378474 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1011 (or 1008 counting only the distinct ones).

The product of its digits is 37632, while the sum is 36.

The square root of 21378474 is about 4623.6861917738. The cubic root of 21378474 is about 277.5399893673.

It can be divided in two parts, 213 and 78474, that added together give a palindrome (78687).

The spelling of 21378474 in words is "twenty-one million, three hundred seventy-eight thousand, four hundred seventy-four".