20431987 has 2 divisors, whose sum is σ = 20431988. Its totient is φ = 20431986.

The previous prime is 20431967. The next prime is 20432017. The reversal of 20431987 is 78913402.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20431987 is a prime.

It is a super-4 number, since 4×20431987⁴ (a number of 30 digits) contains 4444 as substring.

It is not a weakly prime, because it can be changed into another prime (20431967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10215993 + 10215994.

It is an arithmetic number, because the mean of its divisors is an integer number (10215994).

Almost surely, 2^20431987 is an apocalyptic number.

20431987 is a deficient number, since it is larger than the sum of its proper divisors (1).

20431987 is an equidigital number, since it uses as much as digits as its factorization.

20431987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 20431987 is about 4520.1755496883. The cubic root of 20431987 is about 273.3821792869.

The spelling of 20431987 in words is "twenty million, four hundred thirty-one thousand, nine hundred eighty-seven".