21431497 has 2 divisors, whose sum is σ = 21431498. Its totient is φ = 21431496.

The previous prime is 21431489. The next prime is 21431507. The reversal of 21431497 is 79413412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14561856 + 6869641 = 3816^2 + 2621^2 .

It is a cyclic number.

It is not a de Polignac number, because 21431497 - 2³ = 21431489 is a prime.

It is a super-2 number, since 2×21431497² = 918618127322018, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21431197) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715748 + 10715749.

It is an arithmetic number, because the mean of its divisors is an integer number (10715749).

Almost surely, 2^21431497 is an apocalyptic number.

It is an amenable number.

21431497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431497 is an equidigital number, since it uses as much as digits as its factorization.

21431497 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 31.

The square root of 21431497 is about 4629.4164859083. The cubic root of 21431497 is about 277.7692519635.

The spelling of 21431497 in words is "twenty-one million, four hundred thirty-one thousand, four hundred ninety-seven".