21431155 has 8 divisors (see below), whose sum is σ = 25853184. Its totient is φ = 17054400.

The previous prime is 21431149. The next prime is 21431161. The reversal of 21431155 is 55113412.

21431155 = T₃₇₅ + T₃₇₆ + ... + T₅₆₅.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21431149) and next prime (21431161).

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

It is a de Polignac number, because none of the positive numbers 2^k-21431155 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10266 + ... + 12175.

It is an arithmetic number, because the mean of its divisors is an integer number (3231648).

Almost surely, 2^21431155 is an apocalyptic number.

21431155 is a deficient number, since it is larger than the sum of its proper divisors (4422029).

21431155 is a wasteful number, since it uses less digits than its factorization.

21431155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22637.

The product of its digits is 600, while the sum is 22.

The square root of 21431155 is about 4629.3795480604. The cubic root of 21431155 is about 277.7677744249.

Adding to 21431155 its reverse (55113412), we get a palindrome (76544567).

The spelling of 21431155 in words is "twenty-one million, four hundred thirty-one thousand, one hundred fifty-five".