21871837 has 4 divisors (see below), whose sum is σ = 23554300. Its totient is φ = 20189376.

The previous prime is 21871807. The next prime is 21871841. The reversal of 21871837 is 73817812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9803161 + 12068676 = 3131^2 + 3474^2 .

It is a cyclic number.

It is not a de Polignac number, because 21871837 - 2¹⁹ = 21347549 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21871796 and 21871805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21871807) 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, 841212 + ... + 841237.

It is an arithmetic number, because the mean of its divisors is an integer number (5888575).

Almost surely, 2^21871837 is an apocalyptic number.

It is an amenable number.

21871837 is a deficient number, since it is larger than the sum of its proper divisors (1682463).

21871837 is a wasteful number, since it uses less digits than its factorization.

21871837 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1682462.

The product of its digits is 18816, while the sum is 37.

The square root of 21871837 is about 4676.7335823200. The cubic root of 21871837 is about 279.6587552016.

The spelling of 21871837 in words is "twenty-one million, eight hundred seventy-one thousand, eight hundred thirty-seven".