21858401 has 4 divisors (see below), whose sum is σ = 21869232. Its totient is φ = 21847572.

The previous prime is 21858391. The next prime is 21858427. The reversal of 21858401 is 10485812.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21858401 - 2¹⁰ = 21857377 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21858461) 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, 1391 + ... + 6756.

It is an arithmetic number, because the mean of its divisors is an integer number (5467308).

Almost surely, 2^21858401 is an apocalyptic number.

It is an amenable number.

21858401 is a deficient number, since it is larger than the sum of its proper divisors (10831).

21858401 is an equidigital number, since it uses as much as digits as its factorization.

21858401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10830.

The product of its (nonzero) digits is 2560, while the sum is 29.

The square root of 21858401 is about 4675.2968889687. The cubic root of 21858401 is about 279.6014781240.

The spelling of 21858401 in words is "twenty-one million, eight hundred fifty-eight thousand, four hundred one".