261820020 has 96 divisors (see below), whose sum is σ = 914006016. Its totient is φ = 54403200.

The previous prime is 261819989. The next prime is 261820021. The reversal of 261820020 is 20028162.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261820021) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 23716 + ... + 32955.

It is an arithmetic number, because the mean of its divisors is an integer number (9520896).

Almost surely, 2^261820020 is an apocalyptic number.

261820020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261820020 is an abundant number, since it is smaller than the sum of its proper divisors (652185996).

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

261820020 is a wasteful number, since it uses less digits than its factorization.

261820020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56701 (or 56699 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 261820020 is about 16180.8535003565. The cubic root of 261820020 is about 639.7362357103.

Adding to 261820020 its reverse (20028162), we get a palindrome (281848182).

The spelling of 261820020 in words is "two hundred sixty-one million, eight hundred twenty thousand, twenty".