21009770 has 16 divisors (see below), whose sum is σ = 37882080. Its totient is φ = 8389584.

The previous prime is 21009761. The next prime is 21009827. The reversal of 21009770 is 7790012.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5969 + ... + 8811.

It is an arithmetic number, because the mean of its divisors is an integer number (2367630).

Almost surely, 2^21009770 is an apocalyptic number.

21009770 is a deficient number, since it is larger than the sum of its proper divisors (16872310).

21009770 is a wasteful number, since it uses less digits than its factorization.

21009770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3589.

The product of its (nonzero) digits is 882, while the sum is 26.

The square root of 21009770 is about 4583.6415653932. The cubic root of 21009770 is about 275.9351962257.

Adding to 21009770 its reverse (7790012), we get a palindrome (28799782).

The spelling of 21009770 in words is "twenty-one million, nine thousand, seven hundred seventy".