21145280 has 168 divisors, whose sum is σ = 60240672. Its totient is φ = 7028736.

The previous prime is 21145261. The next prime is 21145301. The reversal of 21145280 is 8254112.

21145280 = T₁₇₁ + T₁₇₂ + ... + T₅₀₈.

It is a Harshad number since it is a multiple of its sum of digits (23).

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, 919349 + ... + 919371.

Almost surely, 2^21145280 is an apocalyptic number.

21145280 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 21145280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30120336).

21145280 is an abundant number, since it is smaller than the sum of its proper divisors (39095392).

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

21145280 is a wasteful number, since it uses less digits than its factorization.

21145280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83 (or 60 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21145280 is about 4598.3997216423. The cubic root of 21145280 is about 276.5271727887.

Adding to 21145280 its reverse (8254112), we get a palindrome (29399392).

The spelling of 21145280 in words is "twenty-one million, one hundred forty-five thousand, two hundred eighty".