21361988 has 6 divisors (see below), whose sum is σ = 37383486. Its totient is φ = 10680992.

The previous prime is 21361957. The next prime is 21362041. The reversal of 21361988 is 88916312.

It can be written as a sum of positive squares in only one way, i.e., 17909824 + 3452164 = 4232^2 + 1858^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2670245 + ... + 2670252.

It is an arithmetic number, because the mean of its divisors is an integer number (6230581).

Almost surely, 2^21361988 is an apocalyptic number.

It is an amenable number.

21361988 is a deficient number, since it is larger than the sum of its proper divisors (16021498).

21361988 is a wasteful number, since it uses less digits than its factorization.

21361988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5340501 (or 5340499 counting only the distinct ones).

The product of its digits is 20736, while the sum is 38.

The square root of 21361988 is about 4621.9030712467. The cubic root of 21361988 is about 277.4686294111.

The spelling of 21361988 in words is "twenty-one million, three hundred sixty-one thousand, nine hundred eighty-eight".