20961000 has 192 divisors, whose sum is σ = 75563280. Its totient is φ = 5222400.

The previous prime is 20960999. The next prime is 20961011. The reversal of 20961000 is 16902.

It can be written as a sum of positive squares in 8 ways, for example, as 2762244 + 18198756 = 1662^2 + 4266^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 152932 + ... + 153068.

Almost surely, 2^20961000 is an apocalyptic number.

20961000 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 20961000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37781640).

20961000 is an abundant number, since it is smaller than the sum of its proper divisors (54602280).

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

20961000 is a wasteful number, since it uses less digits than its factorization.

20961000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181 (or 164 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 20961000 is about 4578.3184686083. The cubic root of 20961000 is about 275.7215212572.

Adding to 20961000 its reverse (16902), we get a palindrome (20977902).

The spelling of 20961000 in words is "twenty million, nine hundred sixty-one thousand".