20721887 has 8 divisors (see below), whose sum is σ = 21685536. Its totient is φ = 19779552.

The previous prime is 20721871. The next prime is 20721889. The reversal of 20721887 is 78812702.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20721887 - 2⁴ = 20721871 is a prime.

It is a super-3 number, since 3×20721887³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721889) 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, 3323 + ... + 7244.

It is an arithmetic number, because the mean of its divisors is an integer number (2710692).

Almost surely, 2^20721887 is an apocalyptic number.

20721887 is a deficient number, since it is larger than the sum of its proper divisors (963649).

20721887 is a wasteful number, since it uses less digits than its factorization.

20721887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10657.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 20721887 is about 4552.1299410276. The cubic root of 20721887 is about 274.6690763200.

The spelling of 20721887 in words is "twenty million, seven hundred twenty-one thousand, eight hundred eighty-seven".