21798637 has 4 divisors (see below), whose sum is σ = 24912736. Its totient is φ = 18684540.

The previous prime is 21798631. The next prime is 21798653. The reversal of 21798637 is 73689712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21798637 - 2⁷ = 21798509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21798593 and 21798602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21798631) 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, 1557039 + ... + 1557052.

It is an arithmetic number, because the mean of its divisors is an integer number (6228184).

Almost surely, 2^21798637 is an apocalyptic number.

It is an amenable number.

21798637 is a deficient number, since it is larger than the sum of its proper divisors (3114099).

21798637 is an equidigital number, since it uses as much as digits as its factorization.

21798637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3114098.

The product of its digits is 127008, while the sum is 43.

The square root of 21798637 is about 4668.9010484267. The cubic root of 21798637 is about 279.3464220293.

It can be divided in two parts, 2179 and 8637, that added together give a square (10816 = 104²).

The spelling of 21798637 in words is "twenty-one million, seven hundred ninety-eight thousand, six hundred thirty-seven".