2021721620 has 36 divisors (see below), whose sum is σ = 4438256340. Its totient is φ = 773524224.

The previous prime is 2021721607. The next prime is 2021721629. The reversal of 2021721620 is 261271202.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 1374629776 + 647091844 = 37076^2 + 25438^2 .

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2021721629) 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, 84965 + ... + 106124.

Almost surely, 2^2021721620 is an apocalyptic number.

2021721620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2021721620 is an abundant number, since it is smaller than the sum of its proper divisors (2416534720).

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

2021721620 is a wasteful number, since it uses less digits than its factorization.

2021721620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191144 (or 191119 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 2021721620 is about 44963.5588004330. The cubic root of 2021721620 is about 1264.4658902218.

Adding to 2021721620 its reverse (261271202), we get a palindrome (2282992822).

The spelling of 2021721620 in words is "two billion, twenty-one million, seven hundred twenty-one thousand, six hundred twenty".