21279520 has 48 divisors (see below), whose sum is σ = 50621760. Its totient is φ = 8452864.

The previous prime is 21279497. The next prime is 21279521. The reversal of 21279520 is 2597212.

21279520 = T₂₉₁₅ + T₂₉₁₆ + ... + T₂₉₁₉.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21279521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28269 + ... + 29011.

It is an arithmetic number, because the mean of its divisors is an integer number (1054620).

Almost surely, 2^21279520 is an apocalyptic number.

21279520 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 21279520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25310880).

21279520 is an abundant number, since it is smaller than the sum of its proper divisors (29342240).

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

21279520 is a wasteful number, since it uses less digits than its factorization.

21279520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 937 (or 929 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21279520 is about 4612.9730109768. The cubic root of 21279520 is about 277.1111128736. Note that the first 5 decimals are identical.

The spelling of 21279520 in words is "twenty-one million, two hundred seventy-nine thousand, five hundred twenty".