21777631 has 2 divisors, whose sum is σ = 21777632. Its totient is φ = 21777630.

The previous prime is 21777589. The next prime is 21777641. The reversal of 21777631 is 13677712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21777631 is a prime.

It is a super-2 number, since 2×21777631² = 948530423944322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21777641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10888815 + 10888816.

It is an arithmetic number, because the mean of its divisors is an integer number (10888816).

Almost surely, 2^21777631 is an apocalyptic number.

21777631 is a deficient number, since it is larger than the sum of its proper divisors (1).

21777631 is an equidigital number, since it uses as much as digits as its factorization.

21777631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12348, while the sum is 34.

The square root of 21777631 is about 4666.6509404497. The cubic root of 21777631 is about 279.2566635609.

The spelling of 21777631 in words is "twenty-one million, seven hundred seventy-seven thousand, six hundred thirty-one".