20697840 has 240 divisors, whose sum is σ = 78343200. Its totient is φ = 4866048.

The previous prime is 20697827. The next prime is 20697847. The reversal of 20697840 is 4879602.

20697840 = T₄₀ + T₄₁ + ... + T₄₉₈.

It is a tau number, because it is divible by the number of its divisors (240).

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 = 20697795 and 20697804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20697847) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 232516 + ... + 232604.

It is an arithmetic number, because the mean of its divisors is an integer number (326430).

Almost surely, 2^20697840 is an apocalyptic number.

20697840 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 20697840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39171600).

20697840 is an abundant number, since it is smaller than the sum of its proper divisors (57645360).

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

20697840 is a wasteful number, since it uses less digits than its factorization.

20697840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 135 counting only the distinct ones).

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

The square root of 20697840 is about 4549.4878832677. The cubic root of 20697840 is about 274.5627873533.

The spelling of 20697840 in words is "twenty million, six hundred ninety-seven thousand, eight hundred forty".