21155401 has 4 divisors (see below), whose sum is σ = 21211600. Its totient is φ = 21099204.

The previous prime is 21155399. The next prime is 21155411. The reversal of 21155401 is 10455112.

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 a cyclic number.

It is not a de Polignac number, because 21155401 - 2¹ = 21155399 is a prime.

It is the 4600-th Hogben number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21155411) by changing a digit.

It is a nontrivial repunit in base 4599.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27531 + ... + 28288.

It is an arithmetic number, because the mean of its divisors is an integer number (5302900).

Almost surely, 2^21155401 is an apocalyptic number.

It is an amenable number.

21155401 is a deficient number, since it is larger than the sum of its proper divisors (56199).

21155401 is an equidigital number, since it uses as much as digits as its factorization.

21155401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56198.

The product of its (nonzero) digits is 200, while the sum is 19.

The square root of 21155401 is about 4599.5000815306. The cubic root of 21155401 is about 276.5712848412.

The spelling of 21155401 in words is "twenty-one million, one hundred fifty-five thousand, four hundred one".