21515472 has 180 divisors, whose sum is σ = 71263296. Its totient is φ = 6005760.

The previous prime is 21515449. The next prime is 21515479. The reversal of 21515472 is 27451512.

Its product of digits (2800) is a multiple of the sum of its prime divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515479) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 457753 + ... + 457799.

Almost surely, 2^21515472 is an apocalyptic number.

21515472 is a gapful number since it is divisible by the number (22) 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 21515472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35631648).

21515472 is an abundant number, since it is smaller than the sum of its proper divisors (49747824).

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

21515472 is a wasteful number, since it uses less digits than its factorization.

21515472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106 (or 80 counting only the distinct ones).

The product of its digits is 2800, while the sum is 27.

The square root of 21515472 is about 4638.4773363680. The cubic root of 21515472 is about 278.1315734170.

Adding to 21515472 its reverse (27451512), we get a palindrome (48966984).

The spelling of 21515472 in words is "twenty-one million, five hundred fifteen thousand, four hundred seventy-two".