21361720 has 16 divisors (see below), whose sum is σ = 48063960. Its totient is φ = 8544672.

The previous prime is 21361709. The next prime is 21361721. The reversal of 21361720 is 2716312.

It is a junction number, because it is equal to n+sod(n) for n = 21361691 and 21361700.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21361721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266982 + ... + 267061.

Almost surely, 2^21361720 is an apocalyptic number.

21361720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21361720 is an abundant number, since it is smaller than the sum of its proper divisors (26702240).

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

21361720 is a wasteful number, since it uses less digits than its factorization.

21361720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 534054 (or 534050 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21361720 is about 4621.8740787693. The cubic root of 21361720 is about 277.4674690649.

The spelling of 21361720 in words is "twenty-one million, three hundred sixty-one thousand, seven hundred twenty".