21151431 has 24 divisors (see below), whose sum is σ = 35444864. Its totient is φ = 11903760.

The previous prime is 21151343. The next prime is 21151433. The reversal of 21151431 is 13415112.

It is not a de Polignac number, because 21151431 - 2⁷ = 21151303 is a prime.

It is a super-2 number, since 2×21151431² = 894766066695522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21151433) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1716 + ... + 6726.

Almost surely, 2^21151431 is an apocalyptic number.

21151431 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21151431 is a deficient number, since it is larger than the sum of its proper divisors (14293433).

21151431 is a wasteful number, since it uses less digits than its factorization.

21151431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5091 (or 5088 counting only the distinct ones).

The product of its digits is 120, while the sum is 18.

The square root of 21151431 is about 4599.0684926407. The cubic root of 21151431 is about 276.5539834014.

Adding to 21151431 its reverse (13415112), we get a palindrome (34566543).

The spelling of 21151431 in words is "twenty-one million, one hundred fifty-one thousand, four hundred thirty-one".