21960820 has 36 divisors (see below), whose sum is σ = 53649540. Its totient is φ = 7529088.

The previous prime is 21960811. The next prime is 21960823. The reversal of 21960820 is 2806912.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 10099684 + 11861136 = 3178^2 + 3444^2 .

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21960823) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10225 + ... + 12184.

It is an arithmetic number, because the mean of its divisors is an integer number (1490265).

Almost surely, 2^21960820 is an apocalyptic number.

21960820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21960820 is an abundant number, since it is smaller than the sum of its proper divisors (31688720).

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

21960820 is a wasteful number, since it uses less digits than its factorization.

21960820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22432 (or 22423 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21960820 is about 4686.2372965952. The cubic root of 21960820 is about 280.0374949788.

The spelling of 21960820 in words is "twenty-one million, nine hundred sixty thousand, eight hundred twenty".