20771640 has 96 divisors (see below), whose sum is σ = 70040880. Its totient is φ = 5536512.

The previous prime is 20771633. The next prime is 20771651. The reversal of 20771640 is 4617702.

It is a super-2 number, since 2×20771640² = 862922056579200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8652 + ... + 10788.

Almost surely, 2^20771640 is an apocalyptic number.

20771640 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 20771640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35020440).

20771640 is an abundant number, since it is smaller than the sum of its proper divisors (49269240).

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

20771640 is a wasteful number, since it uses less digits than its factorization.

20771640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2163 (or 2147 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 27.

The square root of 20771640 is about 4557.5914691863. The cubic root of 20771640 is about 274.8887263311. Note that the first 3 decimals are identical.

The spelling of 20771640 in words is "twenty million, seven hundred seventy-one thousand, six hundred forty".