21478901 has 2 divisors, whose sum is σ = 21478902. Its totient is φ = 21478900.

The previous prime is 21478883. The next prime is 21478903. The reversal of 21478901 is 10987412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13498276 + 7980625 = 3674^2 + 2825^2 .

It is a cyclic number.

It is not a de Polignac number, because 21478901 - 2¹⁰ = 21477877 is a prime.

It is a super-2 number, since 2×21478901² = 922686376335602, which contains 22 as substring.

Together with 21478903, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21478903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739450 + 10739451.

It is an arithmetic number, because the mean of its divisors is an integer number (10739451).

Almost surely, 2^21478901 is an apocalyptic number.

It is an amenable number.

21478901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21478901 is an equidigital number, since it uses as much as digits as its factorization.

21478901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21478901 is about 4634.5335256097. The cubic root of 21478901 is about 277.9738990039.

The spelling of 21478901 in words is "twenty-one million, four hundred seventy-eight thousand, nine hundred one".