21259940 has 24 divisors (see below), whose sum is σ = 48080760. Its totient is φ = 7849728.

The previous prime is 21259919. The next prime is 21259957. The reversal of 21259940 is 4995212.

It can be written as a sum of positive squares in 4 ways, for example, as 118336 + 21141604 = 344^2 + 4598^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21259897 and 21259906.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40625 + ... + 41144.

It is an arithmetic number, because the mean of its divisors is an integer number (2003365).

Almost surely, 2^21259940 is an apocalyptic number.

21259940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21259940 is an abundant number, since it is smaller than the sum of its proper divisors (26820820).

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

21259940 is a wasteful number, since it uses less digits than its factorization.

21259940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81791 (or 81789 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 21259940 is about 4610.8502469718. The cubic root of 21259940 is about 277.0260937158.

The spelling of 21259940 in words is "twenty-one million, two hundred fifty-nine thousand, nine hundred forty".