21639474 has 40 divisors (see below), whose sum is σ = 48787200. Its totient is φ = 7168824.

The previous prime is 21639473. The next prime is 21639479. The reversal of 21639474 is 47493612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639473) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 35827 + ... + 36425.

It is an arithmetic number, because the mean of its divisors is an integer number (1219680).

Almost surely, 2^21639474 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21639474, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24393600).

21639474 is an abundant number, since it is smaller than the sum of its proper divisors (27147726).

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

21639474 is a wasteful number, since it uses less digits than its factorization.

21639474 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 836 (or 827 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 21639474 is about 4651.8248032358. The cubic root of 21639474 is about 278.6648768483.

The spelling of 21639474 in words is "twenty-one million, six hundred thirty-nine thousand, four hundred seventy-four".