21811960 has 32 divisors (see below), whose sum is σ = 49572000. Its totient is φ = 8636800.

The previous prime is 21811957. The next prime is 21811987. The reversal of 21811960 is 6911812.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1341 + ... + 6739.

It is an arithmetic number, because the mean of its divisors is an integer number (1549125).

Almost surely, 2^21811960 is an apocalyptic number.

21811960 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21811960 is an abundant number, since it is smaller than the sum of its proper divisors (27760040).

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

21811960 is a wasteful number, since it uses less digits than its factorization.

21811960 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5511 (or 5507 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 21811960 is about 4670.3276116350. The cubic root of 21811960 is about 279.4033212201.

The spelling of 21811960 in words is "twenty-one million, eight hundred eleven thousand, nine hundred sixty".