21390066 has 24 divisors (see below), whose sum is σ = 46619820. Its totient is φ = 7087776.

The previous prime is 21390043. The next prime is 21390071. The reversal of 21390066 is 66009312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21206025 + 184041 = 4605^2 + 429^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 321 + ... + 6548.

Almost surely, 2^21390066 is an apocalyptic number.

21390066 is an abundant number, since it is smaller than the sum of its proper divisors (25229754).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21390066 is a wasteful number, since it uses less digits than its factorization.

21390066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7050 (or 7047 counting only the distinct ones).

The product of its (nonzero) digits is 1944, while the sum is 27.

The square root of 21390066 is about 4624.9395671727. The cubic root of 21390066 is about 277.5901435900.

Adding to 21390066 its reverse (66009312), we get a palindrome (87399378).

The spelling of 21390066 in words is "twenty-one million, three hundred ninety thousand, sixty-six".