20615640 has 64 divisors (see below), whose sum is σ = 62316000. Its totient is φ = 5455872.

The previous prime is 20615629. The next prime is 20615653. The reversal of 20615640 is 4651602.

It is a super-2 number, since 2×20615640² = 850009225219200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 20615640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17304 + ... + 18456.

Almost surely, 2^20615640 is an apocalyptic number.

20615640 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 20615640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31158000).

20615640 is an abundant number, since it is smaller than the sum of its proper divisors (41700360).

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

20615640 is a wasteful number, since it uses less digits than its factorization.

20615640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1316 (or 1312 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 20615640 is about 4540.4449121204. Note that the first 3 decimals coincide. The cubic root of 20615640 is about 274.1988362622.

The spelling of 20615640 in words is "twenty million, six hundred fifteen thousand, six hundred forty".