21388797 has 6 divisors (see below), whose sum is σ = 30894942. Its totient is φ = 14259192.

The previous prime is 21388789. The next prime is 21388799. The reversal of 21388797 is 79788312.

It can be written as a sum of positive squares in only one way, i.e., 15729156 + 5659641 = 3966^2 + 2379^2 .

It is not a de Polignac number, because 21388797 - 2³ = 21388789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388799) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1188258 + ... + 1188275.

It is an arithmetic number, because the mean of its divisors is an integer number (5149157).

Almost surely, 2^21388797 is an apocalyptic number.

It is an amenable number.

21388797 is a deficient number, since it is larger than the sum of its proper divisors (9506145).

21388797 is a wasteful number, since it uses less digits than its factorization.

21388797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2376539 (or 2376536 counting only the distinct ones).

The product of its digits is 169344, while the sum is 45.

The square root of 21388797 is about 4624.8023741561. The cubic root of 21388797 is about 277.5846539878.

The spelling of 21388797 in words is "twenty-one million, three hundred eighty-eight thousand, seven hundred ninety-seven".