21478669 has 2 divisors, whose sum is σ = 21478670. Its totient is φ = 21478668.

The previous prime is 21478663. The next prime is 21478679. The reversal of 21478669 is 96687412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16362025 + 5116644 = 4045^2 + 2262^2 .

It is a cyclic number.

It is not a de Polignac number, because 21478669 - 2³ = 21478661 is a prime.

It is a super-2 number, since 2×21478669² = 922666444023122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21478661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739334 + 10739335.

It is an arithmetic number, because the mean of its divisors is an integer number (10739335).

Almost surely, 2^21478669 is an apocalyptic number.

It is an amenable number.

21478669 is a deficient number, since it is larger than the sum of its proper divisors (1).

21478669 is an equidigital number, since it uses as much as digits as its factorization.

21478669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 43.

The square root of 21478669 is about 4634.5084960544. The cubic root of 21478669 is about 277.9728981740.

It can be divided in two parts, 2147 and 8669, that added together give a square (10816 = 104²).

The spelling of 21478669 in words is "twenty-one million, four hundred seventy-eight thousand, six hundred sixty-nine".