20615421 has 4 divisors (see below), whose sum is σ = 27487232. Its totient is φ = 13743612.

The previous prime is 20615417. The next prime is 20615443. The reversal of 20615421 is 12451602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20615421 - 2² = 20615417 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20615411) 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, 3435901 + ... + 3435906.

It is an arithmetic number, because the mean of its divisors is an integer number (6871808).

Almost surely, 2^20615421 is an apocalyptic number.

It is an amenable number.

20615421 is a deficient number, since it is larger than the sum of its proper divisors (6871811).

20615421 is an equidigital number, since it uses as much as digits as its factorization.

20615421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6871810.

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 20615421 is about 4540.4207954770. The cubic root of 20615421 is about 274.1978653204.

It can be divided in two parts, 206154 and 21, that multiplied together give a palindrome (4329234).

The spelling of 20615421 in words is "twenty million, six hundred fifteen thousand, four hundred twenty-one".