21153971 has 2 divisors, whose sum is σ = 21153972. Its totient is φ = 21153970.

The previous prime is 21153959. The next prime is 21154019. The reversal of 21153971 is 17935112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21153971 - 2²² = 16959667 is a prime.

It is not a weakly prime, because it can be changed into another prime (21153931) by changing a digit.

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 as a sum of consecutive naturals, namely, 10576985 + 10576986.

It is an arithmetic number, because the mean of its divisors is an integer number (10576986).

Almost surely, 2^21153971 is an apocalyptic number.

21153971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21153971 is an equidigital number, since it uses as much as digits as its factorization.

21153971 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1890, while the sum is 29.

The square root of 21153971 is about 4599.3446272268. The cubic root of 21153971 is about 276.5650530859.

The spelling of 21153971 in words is "twenty-one million, one hundred fifty-three thousand, nine hundred seventy-one".