21771020 has 24 divisors (see below), whose sum is σ = 45816624. Its totient is φ = 8689856.

The previous prime is 21771019. The next prime is 21771031. The reversal of 21771020 is 2017712.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21770983 and 21771001.

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, 12227 + ... + 13893.

It is an arithmetic number, because the mean of its divisors is an integer number (1909026).

Almost surely, 2^21771020 is an apocalyptic number.

21771020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21771020 is an abundant number, since it is smaller than the sum of its proper divisors (24045604).

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

21771020 is a wasteful number, since it uses less digits than its factorization.

21771020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2329 (or 2327 counting only the distinct ones).

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 21771020 is about 4665.9425628698. The cubic root of 21771020 is about 279.2284028707.

Adding to 21771020 its reverse (2017712), we get a palindrome (23788732).

The spelling of 21771020 in words is "twenty-one million, seven hundred seventy-one thousand, twenty".