20687940 has 192 divisors, whose sum is σ = 79403520. Its totient is φ = 4354560.

The previous prime is 20687939. The next prime is 20687951. The reversal of 20687940 is 4978602.

It is a super-2 number, since 2×20687940² = 855981722887200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 20687895 and 20687904.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 48930 + ... + 49350.

It is an arithmetic number, because the mean of its divisors is an integer number (413560).

Almost surely, 2^20687940 is an apocalyptic number.

20687940 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 20687940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39701760).

20687940 is an abundant number, since it is smaller than the sum of its proper divisors (58715580).

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

20687940 is a wasteful number, since it uses less digits than its factorization.

20687940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 459 (or 451 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 20687940 is about 4548.3997185823. The cubic root of 20687940 is about 274.5190049250.

The spelling of 20687940 in words is "twenty million, six hundred eighty-seven thousand, nine hundred forty".