21145897 has 4 divisors (see below), whose sum is σ = 21189456. Its totient is φ = 21102340.

The previous prime is 21145871. The next prime is 21145919. The reversal of 21145897 is 79854112.

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 21145897 - 2⁷ = 21145769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21145697) 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, 21043 + ... + 22024.

It is an arithmetic number, because the mean of its divisors is an integer number (5297364).

Almost surely, 2^21145897 is an apocalyptic number.

It is an amenable number.

21145897 is a deficient number, since it is larger than the sum of its proper divisors (43559).

21145897 is an equidigital number, since it uses as much as digits as its factorization.

21145897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43558.

The product of its digits is 20160, while the sum is 37.

The square root of 21145897 is about 4598.4668097095. The cubic root of 21145897 is about 276.5298623662.

It can be divided in two parts, 2114589 and 7, that added together give a triangular number (2114596 = T₂₀₅₆).

The spelling of 21145897 in words is "twenty-one million, one hundred forty-five thousand, eight hundred ninety-seven".