21623040 has 108 divisors (see below), whose sum is σ = 74853324. Its totient is φ = 5763072.

The previous prime is 21622999. The next prime is 21623057. The reversal of 21623040 is 4032612.

It is a happy number.

21623040 is a `hidden beast` number, since 2 + 1 + 623 + 0 + 40 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10653696 + 10969344 = 3264^2 + 3312^2 .

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

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, 10582 + ... + 12458.

Almost surely, 2^21623040 is an apocalyptic number.

21623040 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 21623040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37426662).

21623040 is an abundant number, since it is smaller than the sum of its proper divisors (53230284).

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

21623040 is a wasteful number, since it uses less digits than its factorization.

21623040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1904 (or 1887 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21623040 is about 4650.0580641536. The cubic root of 21623040 is about 278.5943153921.

Adding to 21623040 its reverse (4032612), we get a palindrome (25655652).

The spelling of 21623040 in words is "twenty-one million, six hundred twenty-three thousand, forty".