20721736 has 32 divisors (see below), whose sum is σ = 45354240. Its totient is φ = 8690688.

The previous prime is 20721721. The next prime is 20721737. The reversal of 20721736 is 63712702.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721737) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1305 + ... + 6568.

It is an arithmetic number, because the mean of its divisors is an integer number (1417320).

Almost surely, 2^20721736 is an apocalyptic number.

It is an amenable number.

20721736 is an abundant number, since it is smaller than the sum of its proper divisors (24632504).

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

20721736 is a wasteful number, since it uses less digits than its factorization.

20721736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7933 (or 7929 counting only the distinct ones).

The product of its (nonzero) digits is 3528, while the sum is 28.

The square root of 20721736 is about 4552.1133553549. The cubic root of 20721736 is about 274.6684091489.

The spelling of 20721736 in words is "twenty million, seven hundred twenty-one thousand, seven hundred thirty-six".