21900040 has 16 divisors (see below), whose sum is σ = 49275180. Its totient is φ = 8760000.

The previous prime is 21900031. The next prime is 21900049. The reversal of 21900040 is 4000912.

It is an interprime number because it is at equal distance from previous prime (21900031) and next prime (21900049).

It can be written as a sum of positive squares in 2 ways, for example, as 20088324 + 1811716 = 4482^2 + 1346^2 .

It is a super-2 number, since 2×21900040² = 959223504003200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21899987 and 21900023.

It is not an unprimeable number, because it can be changed into a prime (21900049) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 273711 + ... + 273790.

Almost surely, 2^21900040 is an apocalyptic number.

21900040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21900040 is an abundant number, since it is smaller than the sum of its proper divisors (27375140).

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

21900040 is a wasteful number, since it uses less digits than its factorization.

21900040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 547512 (or 547508 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21900040 is about 4679.7478564555. The cubic root of 21900040 is about 279.7789070998.

Adding to 21900040 its reverse (4000912), we get a palindrome (25900952).

The spelling of 21900040 in words is "twenty-one million, nine hundred thousand, forty".