20211840 has 288 divisors, whose sum is σ = 79361100. Its totient is φ = 4730880.

The previous prime is 20211797. The next prime is 20211847. The reversal of 20211840 is 4811202.

20211840 = 579² + 580² + ... + 633².

It can be written as a sum of positive squares in 2 ways, for example, as 20142144 + 69696 = 4488^2 + 264^2 .

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (20211847) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 696946 + ... + 696974.

Almost surely, 2^20211840 is an apocalyptic number.

20211840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20211840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39680550).

20211840 is an abundant number, since it is smaller than the sum of its proper divisors (59149260).

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

20211840 is a wasteful number, since it uses less digits than its factorization.

20211840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76 (or 50 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 20211840 is about 4495.7580006046. The cubic root of 20211840 is about 272.3967681246.

The spelling of 20211840 in words is "twenty million, two hundred eleven thousand, eight hundred forty".