21871240 has 16 divisors (see below), whose sum is σ = 49210380. Its totient is φ = 8748480.

The previous prime is 21871237. The next prime is 21871243. The reversal of 21871240 is 4217812.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21871237) and next prime (21871243).

It can be written as a sum of positive squares in 2 ways, for example, as 21846276 + 24964 = 4674^2 + 158^2 .

It is a super-2 number, since 2×21871240² = 956702278275200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21871243) 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, 273351 + ... + 273430.

Almost surely, 2^21871240 is an apocalyptic number.

21871240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21871240 is an abundant number, since it is smaller than the sum of its proper divisors (27339140).

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

21871240 is a wasteful number, since it uses less digits than its factorization.

21871240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546792 (or 546788 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21871240 is about 4676.6697552853. The cubic root of 21871240 is about 279.6562107148.

The spelling of 21871240 in words is "twenty-one million, eight hundred seventy-one thousand, two hundred forty".