20997760 has 128 divisors (see below), whose sum is σ = 59241600. Its totient is φ = 6967296.

The previous prime is 20997731. The next prime is 20997761. The reversal of 20997760 is 6779902.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (20997761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 192586 + ... + 192694.

It is an arithmetic number, because the mean of its divisors is an integer number (462825).

Almost surely, 2^20997760 is an apocalyptic number.

20997760 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 20997760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29620800).

20997760 is an abundant number, since it is smaller than the sum of its proper divisors (38243840).

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

20997760 is a wasteful number, since it uses less digits than its factorization.

20997760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178 (or 166 counting only the distinct ones).

The product of its (nonzero) digits is 47628, while the sum is 40.

The square root of 20997760 is about 4582.3312844010. The cubic root of 20997760 is about 275.8826077811.

It can be divided in two parts, 209 and 97760, that added together give a square (97969 = 313²).

The spelling of 20997760 in words is "twenty million, nine hundred ninety-seven thousand, seven hundred sixty".