20631509 has 2 divisors, whose sum is σ = 20631510. Its totient is φ = 20631508.

The previous prime is 20631503. The next prime is 20631547. The reversal of 20631509 is 90513602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18447025 + 2184484 = 4295^2 + 1478^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20631509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20631503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10315754 + 10315755.

It is an arithmetic number, because the mean of its divisors is an integer number (10315755).

Almost surely, 2^20631509 is an apocalyptic number.

It is an amenable number.

20631509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20631509 is an equidigital number, since it uses as much as digits as its factorization.

20631509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 20631509 is about 4542.1920919309. The cubic root of 20631509 is about 274.2691735618.

The spelling of 20631509 in words is "twenty million, six hundred thirty-one thousand, five hundred nine".