21798407 has 4 divisors (see below), whose sum is σ = 21970176. Its totient is φ = 21626640.

The previous prime is 21798389. The next prime is 21798409. The reversal of 21798407 is 70489712.

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

It is a cyclic number.

It is not a de Polignac number, because 21798407 - 2¹⁶ = 21732871 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21798409) 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, 85694 + ... + 85947.

It is an arithmetic number, because the mean of its divisors is an integer number (5492544).

Almost surely, 2^21798407 is an apocalyptic number.

21798407 is a deficient number, since it is larger than the sum of its proper divisors (171769).

21798407 is a wasteful number, since it uses less digits than its factorization.

21798407 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171768.

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 21798407 is about 4668.8764172978. The cubic root of 21798407 is about 279.3454395534.

The spelling of 21798407 in words is "twenty-one million, seven hundred ninety-eight thousand, four hundred seven".