21650040 has 48 divisors (see below), whose sum is σ = 70363800. Its totient is φ = 5773248.

The previous prime is 21650021. The next prime is 21650087. The reversal of 21650040 is 4005612.

It is a happy number.

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

It is a junction number, because it is equal to n+sod(n) for n = 21649995 and 21650022.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29710 + ... + 30429.

Almost surely, 2^21650040 is an apocalyptic number.

21650040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21650040 is an abundant number, since it is smaller than the sum of its proper divisors (48713760).

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

21650040 is a wasteful number, since it uses less digits than its factorization.

21650040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60156 (or 60149 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21650040 is about 4652.9603479935. The cubic root of 21650040 is about 278.7102244385.

Adding to 21650040 its reverse (4005612), we get a palindrome (25655652).

The spelling of 21650040 in words is "twenty-one million, six hundred fifty thousand, forty".