21965820 has 24 divisors (see below), whose sum is σ = 61504464. Its totient is φ = 5857536.

The previous prime is 21965807. The next prime is 21965821. The reversal of 21965820 is 2856912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21965821) 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, 182989 + ... + 183108.

It is an arithmetic number, because the mean of its divisors is an integer number (2562686).

Almost surely, 2^21965820 is an apocalyptic number.

21965820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21965820 is an abundant number, since it is smaller than the sum of its proper divisors (39538644).

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

21965820 is a wasteful number, since it uses less digits than its factorization.

21965820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 366109 (or 366107 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 33.

The square root of 21965820 is about 4686.7707432730. The cubic root of 21965820 is about 280.0587461771.

The spelling of 21965820 in words is "twenty-one million, nine hundred sixty-five thousand, eight hundred twenty".