21771920 has 40 divisors (see below), whose sum is σ = 52258560. Its totient is φ = 8426880.

The previous prime is 21771913. The next prime is 21771977. The reversal of 21771920 is 2917712.

It is a tau number, because it is divible by the number of its divisors (40).

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, 1910 + ... + 6869.

It is an arithmetic number, because the mean of its divisors is an integer number (1306464).

Almost surely, 2^21771920 is an apocalyptic number.

21771920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21771920 is an abundant number, since it is smaller than the sum of its proper divisors (30486640).

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

21771920 is a wasteful number, since it uses less digits than its factorization.

21771920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8823 (or 8817 counting only the distinct ones).

The product of its (nonzero) digits is 1764, while the sum is 29.

The square root of 21771920 is about 4666.0390054092. The cubic root of 21771920 is about 279.2322505254.

The spelling of 21771920 in words is "twenty-one million, seven hundred seventy-one thousand, nine hundred twenty".