21453660 has 240 divisors, whose sum is σ = 76839840. Its totient is φ = 4976640.

The previous prime is 21453659. The next prime is 21453661. The reversal of 21453660 is 6635412.

It is an interprime number because it is at equal distance from previous prime (21453659) and next prime (21453661).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21453661) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 523240 + ... + 523280.

It is an arithmetic number, because the mean of its divisors is an integer number (320166).

Almost surely, 2^21453660 is an apocalyptic number.

21453660 is a gapful number since it is divisible by the number (20) 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 21453660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38419920).

21453660 is an abundant number, since it is smaller than the sum of its proper divisors (55386180).

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

21453660 is a wasteful number, since it uses less digits than its factorization.

21453660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98 (or 87 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 21453660 is about 4631.8095815782. The cubic root of 21453660 is about 277.8649690140.

The spelling of 21453660 in words is "twenty-one million, four hundred fifty-three thousand, six hundred sixty".