20721471 has 4 divisors (see below), whose sum is σ = 27628632. Its totient is φ = 13814312.

The previous prime is 20721461. The next prime is 20721479. The reversal of 20721471 is 17412702.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20721471 - 2⁵ = 20721439 is a prime.

It is a super-3 number, since 3×20721471³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721479) 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, 3453576 + ... + 3453581.

It is an arithmetic number, because the mean of its divisors is an integer number (6907158).

Almost surely, 2^20721471 is an apocalyptic number.

20721471 is a deficient number, since it is larger than the sum of its proper divisors (6907161).

20721471 is an equidigital number, since it uses as much as digits as its factorization.

20721471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6907160.

The product of its (nonzero) digits is 784, while the sum is 24.

The square root of 20721471 is about 4552.0842479023. The cubic root of 20721471 is about 274.6672382779.

The spelling of 20721471 in words is "twenty million, seven hundred twenty-one thousand, four hundred seventy-one".