20661631 has 2 divisors, whose sum is σ = 20661632. Its totient is φ = 20661630.

The previous prime is 20661587. The next prime is 20661643. The reversal of 20661631 is 13616602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20661631 - 2⁹ = 20661119 is a prime.

It is a super-2 number, since 2×20661631² = 853805991160322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20661596 and 20661605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20661691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10330815 + 10330816.

It is an arithmetic number, because the mean of its divisors is an integer number (10330816).

Almost surely, 2^20661631 is an apocalyptic number.

20661631 is a deficient number, since it is larger than the sum of its proper divisors (1).

20661631 is an equidigital number, since it uses as much as digits as its factorization.

20661631 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 20661631 is about 4545.5066824283. The cubic root of 20661631 is about 274.4025863059.

The spelling of 20661631 in words is "twenty million, six hundred sixty-one thousand, six hundred thirty-one".