21497868 has 72 divisors (see below), whose sum is σ = 63408800. Its totient is φ = 6138720.

The previous prime is 21497867. The next prime is 21497881. The reversal of 21497868 is 86879412.

It is not an unprimeable number, because it can be changed into a prime (21497863) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11478 + ... + 13218.

Almost surely, 2^21497868 is an apocalyptic number.

21497868 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21497868, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31704400).

21497868 is an abundant number, since it is smaller than the sum of its proper divisors (41910932).

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

21497868 is a wasteful number, since it uses less digits than its factorization.

21497868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1772 (or 1753 counting only the distinct ones).

The product of its digits is 193536, while the sum is 45.

The square root of 21497868 is about 4636.5793425757. The cubic root of 21497868 is about 278.0556967921.

The spelling of 21497868 in words is "twenty-one million, four hundred ninety-seven thousand, eight hundred sixty-eight".