245721 has 8 divisors (see below), whose sum is σ = 374464. Its totient is φ = 140400.

The previous prime is 245719. The next prime is 245723. The reversal of 245721 is 127542.

It is an interprime number because it is at equal distance from previous prime (245719) and next prime (245723).

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

It is not a de Polignac number, because 245721 - 2¹ = 245719 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 11701 = 245721 / (2 + 4 + 5 + 7 + 2 + 1).

It is an Ulam number.

It is a Duffinian number.

245721 is a lucky number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 245721.

It is not an unprimeable number, because it can be changed into a prime (245723) 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, 5830 + ... + 5871.

It is an arithmetic number, because the mean of its divisors is an integer number (46808).

2²⁴⁵⁷²¹ is an apocalyptic number.

245721 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

245721 is a deficient number, since it is larger than the sum of its proper divisors (128743).

245721 is a wasteful number, since it uses less digits than its factorization.

245721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11711.

The product of its digits is 560, while the sum is 21.

The square root of 245721 is about 495.7025317668. The cubic root of 245721 is about 62.6345687189.

The spelling of 245721 in words is "two hundred forty-five thousand, seven hundred twenty-one".