21012788 has 12 divisors (see below), whose sum is σ = 36899940. Its totient is φ = 10469952.

The previous prime is 21012779. The next prime is 21012821. The reversal of 21012788 is 88721012.

It can be written as a sum of positive squares in 2 ways, for example, as 16467364 + 4545424 = 4058^2 + 2132^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21012788.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7793 + ... + 10136.

It is an arithmetic number, because the mean of its divisors is an integer number (3074995).

Almost surely, 2^21012788 is an apocalyptic number.

It is an amenable number.

21012788 is a deficient number, since it is larger than the sum of its proper divisors (15887152).

21012788 is a wasteful number, since it uses less digits than its factorization.

21012788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18226 (or 18224 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21012788 is about 4583.9707677951. The cubic root of 21012788 is about 275.9484080560.

The spelling of 21012788 in words is "twenty-one million, twelve thousand, seven hundred eighty-eight".