21541979 has 2 divisors, whose sum is σ = 21541980. Its totient is φ = 21541978.

The previous prime is 21541969. The next prime is 21542063. The reversal of 21541979 is 97914512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21541979 - 2⁴ = 21541963 is a prime.

It is not a weakly prime, because it can be changed into another prime (21541909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770989 + 10770990.

It is an arithmetic number, because the mean of its divisors is an integer number (10770990).

Almost surely, 2^21541979 is an apocalyptic number.

21541979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21541979 is an equidigital number, since it uses as much as digits as its factorization.

21541979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 38.

The square root of 21541979 is about 4641.3337522742. Note that the first 3 decimals coincide. The cubic root of 21541979 is about 278.2457456443.

The spelling of 21541979 in words is "twenty-one million, five hundred forty-one thousand, nine hundred seventy-nine".