21520940 has 48 divisors (see below), whose sum is σ = 51916032. Its totient is φ = 7340736.

The previous prime is 21520931. The next prime is 21520949. The reversal of 21520940 is 4902512.

21520940 = T₄₈₃ + T₄₈₄ + ... + T₆₂₂.

It is an interprime number because it is at equal distance from previous prime (21520931) and next prime (21520949).

It is a zygodrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (21520949) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48359 + ... + 48801.

It is an arithmetic number, because the mean of its divisors is an integer number (1081584).

Almost surely, 2^21520940 is an apocalyptic number.

21520940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21520940 is an abundant number, since it is smaller than the sum of its proper divisors (30395092).

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

21520940 is a wasteful number, since it uses less digits than its factorization.

21520940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 806 (or 804 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21520940 is about 4639.0667164851. The cubic root of 21520940 is about 278.1551331236.

The spelling of 21520940 in words is "twenty-one million, five hundred twenty thousand, nine hundred forty".