21612761 has 2 divisors, whose sum is σ = 21612762. Its totient is φ = 21612760.

The previous prime is 21612751. The next prime is 21612769. The reversal of 21612761 is 16721612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20757136 + 855625 = 4556^2 + 925^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21612761 is a prime.

It is a super-2 number, since 2×21612761² = 934222876086242, which contains 22 as substring.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21612761.

It is not a weakly prime, because it can be changed into another prime (21612769) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806380 + 10806381.

It is an arithmetic number, because the mean of its divisors is an integer number (10806381).

Almost surely, 2^21612761 is an apocalyptic number.

It is an amenable number.

21612761 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612761 is an equidigital number, since it uses as much as digits as its factorization.

21612761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1008, while the sum is 26.

The square root of 21612761 is about 4648.9526777544. The cubic root of 21612761 is about 278.5501630303.

The spelling of 21612761 in words is "twenty-one million, six hundred twelve thousand, seven hundred sixty-one".